Update README.md (#667)

README.md

@@ -5,6 +5,8 @@ We are prioritizing this work because we believe this to be the most valuable th
 
 [![appcenterbanner](https://user-images.githubusercontent.com/31293287/32969262-3cc5d48a-cb99-11e7-91bf-fa57c67a371c.png)](http://microsoft.github.io/code-push/)
 
+#### [Sign up With App Center](https://appcenter.ms/signup?utm_source=CodePush&utm_medium=Azure) to use CodePush
+
 # CodePush
 
 [CodePush](https://microsoft.github.io/code-push) is a cloud service that enables Cordova and React Native developers to deploy mobile app updates directly to their users' devices. It works by acting as a central repository that developers can publish updates to (JS, HTML, CSS and images), and that apps can query for updates from (using provided client SDKs for [Cordova](https://github.com/Microsoft/cordova-plugin-code-push) and [React Native](https://github.com/Microsoft/react-native-code-push)). This allows you to have a more deterministic and direct engagement model with your userbase, when addressing bugs and/or adding small features that don't require you to re-build a binary and re-distribute it through the respective app stores.