(Also, I know it's a Microsoft-funded thing, but the animation in the background of the main page runs very poorly on Firefox.)
Looking at the source, reveals:
<link href="/atom.xml" rel="alternate" title="Build New Games" type="application/atom+xml">
Chrome: https://chrome.google.com/webstore/detail/nlbjncdgjeocebhnmk...
Firefox: https://addons.mozilla.org/en-US/firefox/addon/rss-icon/
(Also, I know it's a Microsoft-funded thing, but the animation in the background of the main page runs very poorly on Firefox.)