add "available" extension in Edge Code

You can use these steps to access the Brackets extension listing: https://blogs.adobe.com/edgecode/enabling-the-brackets-extension-registry-in-edge-code/.

Bear in mind that Brackets releases more frequently than Edge Code, so you may find some extensions in the listing that say Edge Code is not new enough to be compatible.  In many cases, Extension Manager will let you install an older, more compatible version of the same extension, though.

- Peter