docs: function shouldPreserveBlock( block ) {
  		return (
  			// #5335
  			block.is( 'pre' ) ||
  			// #5271 - this is a header.
  			headerTagRegex.test( block.getName() ) ||
  			// 11083 - this is a non-editable element.
  			block.getAttribute( 'contenteditable' ) == 'false'
  		);
  	}