Twenty Sixteen: Update theme’s wide image styles to include Image Blocks

Twenty Sixteen includes functionality and styles that make full-size images extend wider than the content when they are added to posts, and appear below the post meta. This update adds the same behavior to image blocks and their captions.

Merges [43911] to trunk.

Props laurelfulford.
Fixes: #45380.
Built from https://develop.svn.wordpress.org/trunk@44263


git-svn-id: https://core.svn.wordpress.org/trunk@44093 1a063a9b-81f0-0310-95a4-ce76da25c4cd