Initialized flipper-plugin library

Summary: Set up an initial library which can (should) be used by plugins in the future.

Reviewed By: jknoxville

Differential Revision: D22019554

fbshipit-source-id: 502b14b34b2c9c117cea377ab6ebbf150e6faee9

desktop/babel-transformer/src/replace-flipper-requires.ts

@@ -17,6 +17,7 @@ import {NodePath} from '@babel/traverse';
 
 const requireReplacements: any = {
   flipper: 'global.Flipper',
+  'flipper-plugin': 'global.FlipperPlugin',
   react: 'global.React',
   'react-dom': 'global.ReactDOM',
   adbkit: 'global.adbkit',