Protect schema.org markup in HTML editor

WordPress HTML editor (tinyMCE) treats schema.org attributes like itemscope/itemtype/itemprop as invalid HTML attributes and strips them when you save the post or page content. This plugin alters this behavior and prevent the WordPress HTML editor from removing the schema.org/microdata markup.

Credits

@azaozz suggested the solution. See the issue discussion here: https://core.trac.wordpress.org/ticket/27931