Enable eslint import checks and fixed the reported errors (#878)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/878

1) Enabled eslint error reporting for unresolved imports and fixed all the errors
2) Enabled eslint for typings (d.ts) and fixed all the errors

Reviewed By: passy

Differential Revision: D20335151

fbshipit-source-id: 7b142281a406b32df0f02a5cd0d7d05eba941acd

desktop/scripts/yarn-install.ts

@@ -16,6 +16,8 @@ const exec = util.promisify(execImport);
 const PACKAGES = [
   'headless-tests',
   'static',
+  'doctor',
+  'pkg',
   'src/plugins/*',
   'src/fb/plugins/*',
   'src/fb/plugins/layout/*',