Summary:
Fixes lots of ESLint warnings. Many of them where in PR #20877 by janicduplessis which requested to split the linting fixes from configuration and package changes.
I solved only the issues that I was most certain about but I would love to get hands on all of them with a little bit of input.
Pull Request resolved: https://github.com/facebook/react-native/pull/22062
Differential Revision: D12889447
Pulled By: TheSavior
fbshipit-source-id: 35f7a08104a5b859c860afdde4af2b32c0685c50
ae8ec39397