GitHub URL Swapper

I got sick of my students sending me a URL for their GitHub repo when I asked for the link to the repo's GitHub Pages site (and vice versa). Click the extension when you're visiting a GitHub Pages site and it will open a new tab with the site's repo. Click the extension when you're visiting a GitHub repo and it will open a new tab with the link for its GitHub Pages site (which will be 404 if GitHub Pages isn't turned on for the repo you're looking at).