added some docs

Author: matt-sanders

src/util.js

@@ -5,6 +5,8 @@ export default exports;
 
 /**
  * Allow additional templates to be added
+ * When they're created they should be prefixed so they don't conflict with native components
+ * eg. addType('input', {}) will be available as <formly_input></formly_input>
  * @param {String} id
  * @param {Object} options
  */