nl_tokens: Create a builder function for marks .
pl_tokens: function mark ( type , attrs ) { return function ( ... args ) { let mark = type . create ( takeAttrs ( attrs , args ) ) let { nodes , tag } = flatten ( type . schema , args , n => <mask> . type . isInSet ( n . marks ) ? n : n . mark ( mark . addToSet ( n . marks ) ) ) return { flat : nodes , tag } } }