Add count of users in view of circle members

lib/screens/circle_editor_screen.dart

@@ -191,7 +191,7 @@ class _CircleEditorScreenState extends State<CircleEditorScreen> {
                   Row(
                     mainAxisAlignment: MainAxisAlignment.spaceBetween,
                     children: [
-                      Text('Circle Members:',
+                      Text('Circle Members (${members.length}):',
                           style: Theme.of(context).textTheme.headlineSmall),
                       IconButton(
                           onPressed: () {