New nodes showcase, mirrors, and theme

A quick word to announce the new nodes section which features repeaters. There is one page per operator, and currently only one operator, but more are welcome!

And speaking of which, a new set of mirrors has been opened. The source code for the site is visible at:

• Codeberg: https://codeberg.org/reseaulibre/lora-reseaulibre-ca/
• sourcehut: https://git.sr.ht/~anarcat/lora.reseaulibre.ca
• GitLab: https://gitlab.com/reseaulibre/lora.reseaulibre.ca
• GitHub: https://github.com/ReseauLibre/lora.reseaulibre.ca

We prefer contributions to come in to Codeberg, but following our spirit of universality and reducing friction for contributions we also accept contributions from the other sites. A more detailed justification of the GitHub is visible here.

Finally, this was done by some work on the site's template, which was made possible by a switch from the old mkdocs-material to Zensical engine. This changed the theme header and some fonts, but the site is mostly similar. The only change is that the git-based change date has been removed while Zensical implements the missing functionality.