Fix text attachments in release android form apps

Apps/Contoso.Forms.Demo/Contoso.Forms.Demo/Views/TextAttachmentView.xaml.cs

@@ -4,6 +4,7 @@ using Xamarin.Forms;
 
 namespace Contoso.Forms.Demo.Views
 {
+    [Android.Runtime.Preserve(AllMembers = true)]
     public partial class TextAttachmentView : ContentPage
     {
         private readonly TaskCompletionSource<string> _taskCompletionSource = new TaskCompletionSource<string>();

Apps/Contoso.Forms.Puppet/Contoso.Forms.Puppet/Views/TextAttachmentView.xaml.cs

@@ -4,6 +4,7 @@ using Xamarin.Forms;
 
 namespace Contoso.Forms.Puppet.Views
 {
+    [Android.Runtime.Preserve(AllMembers = true)]
     public partial class TextAttachmentView : ContentPage
     {
         private readonly TaskCompletionSource<string> _taskCompletionSource = new TaskCompletionSource<string>();