WordPress 5/Gutenberg: Activate only specific block types

listing-6-3.php

/**
 * Allow only certain block types in Gutenberg
 * Possible:
  * core/list, core/quote, core/cover-image, core/paragraph, core/image, core/heading, core/gallery, core/audio, core/file, core/video
  * core/freeform, core/html, core/code, core/preformatted, core/pullquote, core/table, core/verse
  * core/button, core/text-columns, core/more, core/nextpage, core/separator, core/spacer
  * core/shortcode, core/archives, core/categories, core/latest-comments, core/latest-posts
  * core-embed/: twitter, youtube, facebook, Instagram, wordpress, soundcloud, spotify, flickr, vimeo, animoto, cloudup, collegehumor, dailymotion, funnyordie, hulu, imgur, issuu, kickstarter, meetup-com, mixcloud, photobucket, polldaddy, reddit, reverbnation, screencast, sribd, slideshare, smugmug, speaker, ted, tumblr, videopress, wordpress-tv
 */
function my_allowed_block_types( $allowed_blocks ) {
 	return array(
		'core/image',
		'core/paragraph',
		'core/heading',
	); 
}
add_filter( 'allowed_block_types', 'my_allowed_block_types' );