New Example - Firebase Google Authentication (#106)

* Added the firebase+google_authentication example

* Modified Readme.md

firebase_google_authentication/lib/main.dart

@@ -0,0 +1,26 @@
+import 'package:firebase_core/firebase_core.dart';
+import 'package:firebase_google_authentication/Screens/HomePage.dart';
+import 'package:firebase_google_authentication/Services/google_auth.dart';
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+
+void main() async{
+  WidgetsFlutterBinding.ensureInitialized();
+  await Firebase.initializeApp();
+  runApp(MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return ChangeNotifierProvider(
+      create: (context) => GoogleSignInProvider(),
+      child: MaterialApp(
+        debugShowCheckedModeBanner: false,
+        home: HomePage(),
+      ),
+    );
+  }
+}