[skip-ci] update comment for Polymer.html

lib/utils/html-fn.html

@@ -25,9 +25,15 @@
     }
 
     /**
-     * Small tagged template string function to facilitate building a `<template>` element.
-     * Polymer.html will automatically compose `<template>` elements in `${}` blocks, allowing for easy
-     * composition of superclass templates, or partial templates.
+     * A template literal tag1 that creates an HTML <template> element from the contents of the string.
+     *
+     * This allows you to write a Polymer Template in JavaScript.
+     *
+     * Interpolated values are converted to strings when the template is created,
+     * they are not intended as a replacement for Polymer data-binding.
+     *
+     * There is special support for HTMLTemplateElement values,
+     * allowing for easy composition of superclass or partial templates.
      *
      * Example:
      *