Include ExpandingTextareas in plugins.jquery.com

This is pretty easy and might make this plugin more discoverable.

Essentially, you'd need to connect the repo to the jQuery Plugin Registry via webhook, publish a [valid manifest file][1] and then bump the version to trigger a registry update.

Full instructions here: <http://plugins.jquery.com/docs/publish/>

[1]: http://plugins.jquery.com/docs/package-manifest/