Introduce useLogger hook

Summary: In the Flipper chrome there is a lot of `logger={logger}` prop drilling. Let's not do that anymore in the future by using a proper hook, which is exposed from `flipper-plugin`.

Reviewed By: passy

Differential Revision: D25421304

fbshipit-source-id: 01ec8563c67f7e2fac359c2f8216eba722bff8d9

desktop/flipper-plugin/src/index.ts

@@ -62,6 +62,13 @@ export {
 } from './ui/Tracked';
 
 export {sleep} from './utils/sleep';
+export {
+  LogTypes,
+  TrackType,
+  Logger,
+  useLogger,
+  _LoggerContext,
+} from './utils/Logger';
 
 // It's not ideal that this exists in flipper-plugin sources directly,
 // but is the least pain for plugin authors.