Docs: Add a mention of `core-block-patterns` as a possible value for `add_theme_support()`.

Follow-up to [48492].

See #50669.
Built from https://develop.svn.wordpress.org/trunk@48598


git-svn-id: https://core.svn.wordpress.org/trunk@48360 1a063a9b-81f0-0310-95a4-ce76da25c4cd