Adding shrine. (#3)

Adds a new version of Shrine from the MDC codelabs.

shrine/ios/Runner/AppDelegate.m

@@ -0,0 +1,13 @@
+#include "AppDelegate.h"
+#include "GeneratedPluginRegistrant.h"
+
+@implementation AppDelegate
+
+- (BOOL)application:(UIApplication *)application
+    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
+  [GeneratedPluginRegistrant registerWithRegistry:self];
+  // Override point for customization after application launch.
+  return [super application:application didFinishLaunchingWithOptions:launchOptions];
+}
+
+@end