// Enqueue an override script (in functions.php)
wp_enqueue_script('strattic-prismatic', get_stylesheet_directory_uri() . '/js/prismatic-override.js', array( 'wp-hooks', 'wp-i18n', 'wp-blocks', 'wp-dom' ), $theme->get('Version'), true );

===
  
// This is the prismatic-override.js file
wp.hooks.addFilter('prismJsLanguages', 'prismatic/blocks', function(languages){
	return [
		{ label : 'Language..',    value : '' },
		{ label : 'PHP',           value : 'php' },
		{ label : 'JavaScript',    value : 'javascript' },
		{ label : 'HTML',          value : 'markup' },
		{ label : 'JSON',          value : 'json' },
		{ label : 'YAML',          value : 'yaml' }
	];
});