Convert plugin.js to plugin.tsx

Summary:
* Deletes plugin.js
* Adds plugin.tsx
* Adds plugin flow-typed module that has the old flow types

Reviewed By: passy

Differential Revision: D16668067

fbshipit-source-id: b2f0ce47c4cf7125b4e352821e921b97675d12a9

src/plugins/network/index.js

@@ -35,7 +35,7 @@ import {
 import RequestDetails from './RequestDetails.js';
 import {clipboard} from 'electron';
 import {URL} from 'url';
-import type {Notification} from '../../plugin';
+import type {Notification} from '../../plugin.tsx';
 
 type PersistedState = {|
   requests: {[id: RequestId]: Request},