This introduces the Block Bindings API for WordPress.
The API allows developers to connects block attributes to different sources. In this PR, two such sources are included: "post meta" and "pattern". Attributes connected to sources can have their HTML replaced by values coming from the source in a way defined by the binding.
Props czapla, lgladdy, gziolo, sc0ttkclark, swissspidy, artemiosans, kevin940726, fabiankaegy, santosguillamot, talldanwp, wildworks.
Fixes#60282.
git-svn-id: https://develop.svn.wordpress.org/trunk@57514 602fd350-edb4-49c9-b593-d223f7449a82