function requireIterator () {
	if (hasRequiredIterator) return iterator;
	hasRequiredIterator = 1;
	iterator = function (Yallist) {
	  Yallist.prototype[Symbol.iterator] = function* () {
	    for (let walker = this.head; walker; walker = walker.next) {
	      yield walker.value;
	    }
	  };
	};
	return iterator;
}
Check if `mime` is text and should be buffered.

@param {String} mime
@return {Boolean}
@api public