Updated README with more descriptions of samples and key branches

Author: cy245

README.md

@@ -3,3 +3,20 @@ Android Identity Samples Repository
 
 This repository contains a set of individual Android Studio projects to help you get
 started writing/understanding Android identity features.
+
+There are 2 main branches, `main` and `credman-compose`.
+
+Branch `main` contains the primary samples for Credential Manager:
+* `CredentialManager` - Simple app demonstrating how to use basic Credential Manager functions
+* `CredentialProvider/MyVault` - Simple credential provider app implementation
+* `SmsVerification` - Legacy sample using Play Service's SMS Verification APIs
+* `WebView` - Contains 2 folders. `CredentialManagerWebView` contains code snippets to use
+  Credential Manager with WebView. `WebkitWebView` contains a sample app that uses the Webkit
+  library to implement passkey creation in WebView
+
+Branch `credman-compose` notably contains 2 `Shrine` samples:
+* `Shrine` is a more developed mobile app featuring best practices and recommended UX when
+  using Credential Manager. The sample features multiple methods of sign-up, sign-in, settings
+  configuration, and session management.
+* `Shrinewear/appkt` is a Wear app that works together with the Shrine mobile app. It features
+  seamless authentication via passkey and Sign-in-with-Google logins.