Make plugin loading async

Summary: This diff makes plugin loading async, which we'd need in a browser env (either because we'd use `import()` or we need to fetch the source and than eval it), and deals with all the fallout of that

Reviewed By: timur-valiev

Differential Revision: D32669995

fbshipit-source-id: 73babf38a6757c451b8200c3b320409f127b8b5b

desktop/app/src/electron/initializeElectron.tsx

@@ -177,6 +177,9 @@ export function initializeElectron(
       return flipperServerConfig.gatekeepers[gatekeeper] ?? false;
     },
     flipperServer,
+    async requirePlugin(path) {
+      return (window as any).electronRequire(path);
+    },
   } as RenderHost;
 
   setupMenuBar();