Summary:
This converts the index file to TypeScript which is used as an export for all plugins. Alongside, I had to fix a couple of errors in various files to make sure everything works correctly.
For plugins using flow, we define an interface which uses the type definition for FlipperPlugin and types all UI components as `any`.
Reviewed By: passy
Differential Revision: D16936890
fbshipit-source-id: dacd9a63a82b9f0bbb530b06072186874cba7b6f
