Support handling deeplinks in plugins

Summary:
This adds support for handling incoming deeplinks in a Sandy plugin, which can be done by using a `client.onDeepLink(deepLink => { } )` listener

Also generalized deeplinks to not just support strings, but also richer objects, which is beneficial to plugin to plugin linking.

Reviewed By: jknoxville

Differential Revision: D22524749

fbshipit-source-id: 2cbe8d52f6eac91a1c1c8c8494706952920b9181

desktop/plugins/network/index.tsx

@@ -273,10 +273,10 @@ export default class extends FlipperPlugin<State, any, PersistedState> {
   };
 
   parseDeepLinkPayload = (
-    deepLinkPayload: string | null,
+    deepLinkPayload: unknown,
   ): Pick<State, 'selectedIds' | 'searchTerm'> => {
     const searchTermDelim = 'searchTerm=';
-    if (deepLinkPayload === null) {
+    if (typeof deepLinkPayload !== 'string') {
       return {
         selectedIds: [],
         searchTerm: '',