Summary: This diffs refactors tsc projects structure and structure of our custom typings to allow producing typescript typings for "flipper" package. In next diffs I'm going to use the produced typings to check compatibility of plugins with certain versions of Flipper, e.g. to check whether plugin is compatible with current "stable" and "insiders" version.
Reviewed By: passy
Differential Revision: D26997158
fbshipit-source-id: a0416c7139bf08ec9d175730da4c4c2a8768eeb7
f468f0e07d