Post-Hugo-migration quick fixes

Just cataloging things I find that I can quickly fix later: - [x] Add /books/ page with list of my books. - [x] About page links to 'my books' and 'blog' both need updating. - [x] Add a favicon (I think I used to have one... just don't remember if I have it stashed in the old Drupal codebase) - [x] Add a `robots.txt` file - [x] Search for `/blogs/jeff-geerling` and make sure if there's a `drupal.path` for that, there's also an `aliases` entry for Hugo since that won't line up with the default blog path/slug. - [x] Browse blog post in light mode — related content and comments boxes are both dark backgrounds with dark text, and that should *not* be the case! - [x] Fix [tag links going to non-canonical location](https://github.com/athul/archie/issues/154) (without trailing slash) - [x] Redirect `/rss.xml` to `/blog.xml` (Apache .htaccess) - [x] Monitor goaccess logs for 404s: `sudo goaccess /var/log/apache2/other_vhosts_access.log --log-format=COMBINED_VHOST -d`