prettier 2

Summary:
Quick notes:

- This looks worse than it is. It adds mandatory parentheses to single argument lambdas. Lots of outrage on Twitter about it, personally I'm {emoji:1f937_200d_2642} about it.
- Space before function, e.g. `a = function ()` is now enforced. I like this because both were fine before.
- I added `eslint-config-prettier` to the config because otherwise a ton of rules conflict with eslint itself.

Close https://github.com/facebook/flipper/pull/915

Reviewed By: jknoxville

Differential Revision: D20594929

fbshipit-source-id: ca1c65376b90e009550dd6d1f4e0831d32cbff03

desktop/plugins/example/index.tsx

@@ -102,7 +102,7 @@ export default class Example extends FlipperPlugin<State, any, PersistedState> {
         <Text>{this.state.prompt}</Text>
         <Input
           placeholder="Message"
-          onChange={event => {
+          onChange={(event) => {
             this.setState({message: event.target.value});
           }}
         />