Added covid-19 example app and Updated the readme (#73)

covid19_mobile_app/lib/widgets/drawer.dart

@@ -0,0 +1,40 @@
+import '../screens/home.dart';
+import '../screens/countrylist.dart';
+import 'package:flutter/material.dart';
+
+class DrawerWidget extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return Drawer(
+      child: ListView(
+        // Important: Remove any padding from the ListView.
+        padding: EdgeInsets.zero,
+        children: <Widget>[
+          Container(
+            child: Image.asset('assets/virus.gif'),
+          ),
+          ListTile(
+            leading: CircleAvatar(
+              child: Image.asset("assets/logo.png"),
+            ),
+            title: Text('Home'),
+            onTap: () {
+              Navigator.pushReplacement(
+                  context, MaterialPageRoute(builder: (context) => Home()));
+            },
+          ),
+          ListTile(
+            leading: CircleAvatar(
+              child: Image.asset("assets/logo.png"),
+            ),
+            title: Text('Affected Countries'),
+            onTap: () {
+              Navigator.pushReplacement(context,
+                  MaterialPageRoute(builder: (context) => CountryList()));
+            },
+          ),
+        ],
+      ),
+    );
+  }
+}