New Example - Firebase Google Authentication (#106)

* Added the firebase+google_authentication example

* Modified Readme.md

firebase_google_authentication/lib/Screens/InfoPage.dart

@@ -0,0 +1,64 @@
+import 'package:firebase_auth/firebase_auth.dart';
+import 'package:firebase_google_authentication/Services/google_auth.dart';
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+
+class InfoPage extends StatefulWidget {
+  const InfoPage({Key? key}) : super(key: key);
+
+  @override
+  _InfoPageState createState() => _InfoPageState();
+}
+
+class _InfoPageState extends State<InfoPage> {
+  @override
+  Widget build(BuildContext context) {
+    User? user = FirebaseAuth.instance.currentUser;
+    return SafeArea(
+      child: Scaffold(
+        body: Column(
+          mainAxisAlignment: MainAxisAlignment.start,
+          children: [
+            Row(
+              mainAxisAlignment: MainAxisAlignment.end,
+              children: [
+                FlatButton(onPressed: (){
+                  final provider = Provider.of<GoogleSignInProvider>(
+                      context,
+                      listen: false);
+                  provider.googleLogout();
+                },
+                    child: Text('Logout',
+                      style: TextStyle(
+                        color: Colors.blue,
+                        fontSize: 16,
+                      ),
+                    )),
+              ],
+            ),
+            SizedBox(height: 200,),
+            Column(
+              mainAxisAlignment: MainAxisAlignment.center,
+              //crossAxisAlignment: CrossAxisAlignment.center,
+              children: [
+                CircleAvatar(
+                  radius: 40,
+                  backgroundImage: NetworkImage(
+                    user!.photoURL??'https://cdn.pixabay.com/photo/2015/10/05/22/37/blank-profile-picture-973460_1280.png'
+                  ),
+                ),
+                SizedBox(height: 15,),
+                Text(user!.email??'',
+                  style: TextStyle(
+                    fontSize: 18,
+                    fontWeight: FontWeight.w500
+                  ),
+                ),
+              ],
+            )
+          ],
+        ),
+      ),
+    );
+  }
+}