Add deprecation warning to RCTBatchedBridge

Reviewed By: fkgozali

Differential Revision: D5553607

fbshipit-source-id: 94a69264231c4adc1648e34ad64833f042e0d4db

React/Base/RCTBatchedBridge.mm

@@ -538,6 +538,11 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
       [[NSNotificationCenter defaultCenter]
        postNotificationName:RCTJavaScriptDidLoadNotification
        object:self->_parentBridge userInfo:@{@"bridge": self}];
+
+#if RCT_DEV
+      RCTLogWarn(@"RCTBatchedBridge is deprecated and will be removed in a future React Native release. "
+        "See https://fb.me/react-cxx-bridge for upgrade instructions.");
+#endif
     });
 
     [self _flushPendingCalls];