Summary:
My changes in https://github.com/facebook/react-native/pull/13707 assumed RN website works the same way as React website, but this assumption was wrong, so I added invalid markup.
This fixes it, and also moves the images into the website folder so we don't depend on random CDNs.
Closes https://github.com/facebook/react-native/pull/13844
Differential Revision: D5019956
Pulled By: gaearon
fbshipit-source-id: bec40d70997231a73d3ef67c82386bc1bb202d7b