add readmes for all sample folders in the solution (#8)

* Add readmes+screenshots

DragAndDrop and IntentToSecondScreen

* Add Xamarin.Forms readme+screenshots

* add READMEs for UX samples

* add screenshots and Xamarin.Android link

* minor updates to text

CompanionPane/README.md

@@ -0,0 +1,11 @@
+# CompanionPane sample for Surface Duo with Xamarin.Android
+
+Read about the [Companion pane user experience](https://docs.microsoft.com/dual-screen/introduction#companion-pane) and visit the [docs page](https://docs.microsoft.com/dual-screen/android/sample-code/companion-pane) for more information.
+
+![Companion pane sample](Screenshots/companion-pane-500.png)
+
+## Related links
+
+- [Introduction to dual-screen devices](https://docs.microsoft.com/dual-screen/introduction)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)
+- [Xamarin.Android documentation](https://docs.microsoft.com/xamarin/android/)

DragAndDrop/README.md

@@ -0,0 +1,12 @@
+# Drag and drop sample for Surface Duo (using C# and Xamarin)
+
+Visit the [drag and drop docs page](https://docs.microsoft.com/dual-screen/android/sample-code/drag-drop/) for more information.
+
+To test drag and drop behavior, drag the image or text from the left screen onto the target areas on the right:
+
+![Drag and drop sample](Screenshots/drag-drop-500.png)
+
+## Related links
+
+- [Drag and drop for Surface Duo doc](https://docs.microsoft.com/dual-screen/android/sample-code/drag-drop/)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)

DualView/README.md

@@ -0,0 +1,11 @@
+# DualView sample for Surface Duo with Xamarin.Android
+
+Read about the [Dual view user experience](https://docs.microsoft.com/dual-screen/introduction#dual-view) and visit the [docs page](https://docs.microsoft.com/dual-screen/android/sample-code/dual-view) for more information.
+
+![Dual view sample spanned across two screens](Screenshots/dual-view-500.png)
+
+## Related links
+
+- [Introduction to dual-screen devices](https://docs.microsoft.com/dual-screen/introduction)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)
+- [Xamarin.Android documentation](https://docs.microsoft.com/xamarin/android/)

ExtendCanvas/README.md

@@ -0,0 +1,11 @@
+# ExtendCanvas sample for Surface Duo with Xamarin.Android
+
+Read about the [Extended Canvas user experience](https://docs.microsoft.com/dual-screen/introduction#extended-canvas) and visit the [docs page](https://docs.microsoft.com/dual-screen/android/sample-code/extended-canvas) for more information.
+
+![Extended canvas sample spanned across two screens](Screenshots/extended-canvas-500.png)
+
+## Related links
+
+- [Introduction to dual-screen devices](https://docs.microsoft.com/dual-screen/introduction)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)
+- [Xamarin.Android documentation](https://docs.microsoft.com/xamarin/android/)

IntentToSecondScreen/README.md

@@ -0,0 +1,38 @@
+# Intent to second screen sample for Surface Duo (using C# and Xamarin)
+
+This sample demonstrates how to cause an activity to open on the second screen (as long as it's empty, otherwise the activity will launch over the current one).
+
+In the main activity, choose an option to start: another activity from the current app or a URL in a browser window:
+
+![Intent to second screen menu](Screenshots/intent-second-screen-menu-500.png)
+
+If the launcher is still visible on the other screen, the new activity will appear there:
+
+![Intent opened on second screen](Screenshots/intent-second-screen-500.png)
+
+The sample uses these functions to set the intent flags required to start on the second screen if available:
+
+```csharp
+void StartIntentSecondActivity()
+{
+    var intent = new Intent(this, typeof(SecondActivity));
+    // Intent.FLAG_ACTIVITY_LAUNCH_ADJACENT is required to launch a second activity
+    // on a second display while still keeping the first activity on the first display
+    // (not pausing/stopping it)
+    intent.AddFlags(ActivityFlags.LaunchAdjacent | ActivityFlags.NewTask);
+    StartActivity(intent);
+}
+
+void StartIntentBrowserApp(string url)
+{
+    var intent = new Intent(Intent.ActionView, Android.Net.Uri.Parse(url));
+    intent.AddFlags(ActivityFlags.LaunchAdjacent | ActivityFlags.NewTask);
+    StartActivity(intent);
+}
+```
+
+## Related links
+
+- [Launch intent to second screen docs](https://docs.microsoft.com/dual-screen/android/sample-code/launch-to-second-screen/)
+- [Introduction to dual-screen devices](https://docs.microsoft.com/dual-screen/introduction)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)

MasterDetail/README.md

@@ -0,0 +1,11 @@
+# List-detail sample for Surface Duo with Xamarin.Android
+
+Read about the [List detail user experience](https://docs.microsoft.com/dual-screen/introduction#list-detail) and visit the [docs page](https://docs.microsoft.com/dual-screen/android/sample-code/list-detail) for more information.
+
+![List detail example spanned across two screens](Screenshots/list-detail-500.png) ![List detail on a single screen](Screenshots/list-detail-250.png)
+
+## Related links
+
+- [Introduction to dual-screen devices](https://docs.microsoft.com/dual-screen/introduction)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)
+- [Xamarin.Android documentation](https://docs.microsoft.com/xamarin/android/)

TwoPage/README.md

@@ -0,0 +1,11 @@
+# TwoPage sample for Surface Duo with Xamarin.Android
+
+Read about the [Two Page user experience](https://docs.microsoft.com/dual-screen/introduction#two-page) and visit the [docs page](https://docs.microsoft.com/dual-screen/android/sample-code/two-page) for more information.
+
+![Two Page example spanned across two screens](Screenshots/two-page-500.png)
+
+## Related links
+
+- [Introduction to dual-screen devices](https://docs.microsoft.com/dual-screen/introduction)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)
+- [Xamarin.Android documentation](https://docs.microsoft.com/xamarin/android/)

XamarinForms/README.md

@@ -0,0 +1,23 @@
+# Xamarin.Forms sample for Surface Duo
+
+This solution contains two projects:
+
+- **DualScreenDemos** - the Xamarin.Forms shared-code for this sample.
+- **DualScreenDemos.Android** - the Android app (set this as the Startup Project).
+
+The code uses the [Xamarin.Forms.DualScreen](https://www.nuget.org/packages/Xamarin.Forms.DualScreen/) NuGet package to enable Surface Duo-specific dual-screen functionality.
+
+The menu of options available in the sample is shown below. It includes basic demonstrations of each of the five [dual-screen UX patterns](https://docs.microsoft.com/dual-screen/introduction#dual-screen-app-patterns) as well as the TwoPaneView playground:
+
+![Surface Duo sample app menu](Screenshots/xamarin-forms-menu-500.png)
+
+The TwoPaneView control is a new layout optimized for the Surface Duo, but which provides a powerful split-view control that works on all platforms:
+
+![Surface Duo Xamarin.Forms TwoPaneView demo screen](Screenshots/xamarin-forms-twopaneview-500.png)
+
+## Related links
+
+- [Introduction to dual-screen devices](https://docs.microsoft.com/dual-screen/introduction)
+- [Get the Surface Duo emulator](https://docs.microsoft.com/dual-screen/android/emulator/)
+- [Surface Duo Xamarin developer docs](https://docs.microsoft.com/dual-screen/xamarin/)
+- [Xamarin.Forms docs](https://docs.microsoft.com/xamarin/xamarin-forms/app-fundamentals/dual-screen/)