~This extension doesn’t work from Firefox 57 on. I might update it when I find time.~
Ever wanted to view HTML pages directly from GitHub? Me too. Unfortunately the Raw button doesn’t render the HTML but only displays the source code. There are a bunch of Chrome extensions that add a button to open file from Github at rawgit directly, but none for Firefox. So I wrote one. It’s still an early version and more of a hack than a real extension, but it works (mostly).