This update adds styles and theme support related to the new block-based editor to enhance the experience of using it with Twenty Fifteen.
These are the specific changes made to this theme:
* Add blocks.css, to style blocks on the front end, to make sure they match the theme’s existing HTML element styles.
* Add editor-blocks.css to style blocks in the editor, to make sure they match the theme’s existing HTML element styles.
* Add theme support for `editor-styles`, to pull the existing editor stylesheet into the new editor.
* Add theme support for `wp-block-styles`, to load the default block styles on the front end.
* Add theme support for `editor-color-palette`, to load a color palette based on the theme’s color scheme into the block-based editor.
Props laurelfulford.
Fixes#45043.
Built from https://develop.svn.wordpress.org/branches/5.0@43798
git-svn-id: http://core.svn.wordpress.org/branches/5.0@43627 1a063a9b-81f0-0310-95a4-ce76da25c4cd
David A. Kennedy