Allow Deeplinking via Linking.getInitialURL() (facebook#44552)

Summary:
Pull Request resolved: facebook#44552

Changelog: [Android][Fixed] If the RNTester app is started with a deeplink intent, we now correctly navigate there for Android to facilitate e2e testing. This already worked on ios.

Reviewed By: javache

Differential Revision: D54662737

fbshipit-source-id: 5bbf824c80e226f441bdcbc4fa67e41ab4c3eb33

Author: GijsWeterings

packages/rn-tester/js/RNTesterAppShared.js

@@ -199,6 +199,10 @@ const RNTesterApp = ({
     [dispatch],
   );
   React.useEffect(() => {
+    // Initial deeplink
+    Linking.getInitialURL()
+      .then(url => url != null && handleOpenUrlRequest({url: url}))
+      .catch(_ => {});
     const subscription = Linking.addEventListener('url', handleOpenUrlRequest);
     return () => subscription.remove();
   }, [handleOpenUrlRequest]);