Summary:
The lack of very clear docs on supported image formats is causing unnecessary issues (#13806).
This should mitigate and keep the issue list cleaner.
Its only a documentation change. No code changes made.
Closes https://github.com/facebook/react-native/pull/13807
Differential Revision: D5023002
Pulled By: javache
fbshipit-source-id: b1e3562ae7649cf71833b300e125966d6e832a69