sidebar: Add rel="me" to Mastodon link
Then Mastodon can indicate that I do in fact own the site.
Many small changes
* Some minor style editing
* Provide a "Go back" button on post pages to return to the index
* Redo sites.md a little
Another step in the overhaul
First steps in a complete overhaul of the website
Get rid of a bunch of annoying frameworks, stick to SCSS and use the
grid system. The layout is *heavily* inspired by
https://drewdevault.com/ - it just looks really neat.