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/app/src/ui/components/Markdown.tsx

@@ -21,7 +21,7 @@ const Row = styled.div({
   marginBottom: 5,
   lineHeight: 1.34,
 });
-const Heading = styled.div<{level: number}>(props => ({
+const Heading = styled.div<{level: number}>((props) => ({
   fontSize: props.level === 1 ? 18 : 12,
   textTransform: props.level > 1 ? 'uppercase' : undefined,
   color: props.level > 1 ? '#90949c' : undefined,