- First pass at adding the site editor from the Gutenberg plugin to
wp-admin/site-editor.php.
- Adds miscellaneous PHP changes from Gutenberg 10.1 - 11.9.
Follows [52042].
See #54337.
Props youknowriad, aristath, hellofromtonya, gziolo.
git-svn-id: https://develop.svn.wordpress.org/trunk@52069 602fd350-edb4-49c9-b593-d223f7449a82