feat: add watch signed in user extension

Author: Peter Gordon Hayes

lib/lit_firebase_auth.dart

@@ -1,5 +1,6 @@
 export 'src/domain/auth/auth_providers.dart';
 export 'src/domain/auth/i_auth_facade.dart';
+export 'src/domain/auth/user.dart';
 export 'src/infrastructure/firebase_auth_facade.dart';
 export 'src/presentation/core/auth_config.dart';
 export 'src/presentation/core/extensions.dart';

lib/src/presentation/core/extensions.dart

@@ -110,4 +110,8 @@ extension AuthContext on BuildContext {
   User getSignedInUser() {
     return Provider.of<User>(this, listen: false);
   }
+
+  User watchSignedInUser() {
+    return Provider.of<User>(this);
+  }
 }