Matrix notifications

[zeuner]

According to some quick survey (https://discourse.nixos.org/t/accessibility-and-obstacles-to-community-contribution/32845/37), quite a fraction would like to be notified about packages they maintain using other means than GitHub. This can also be expected considering that the maintainer list (https://github.com/NixOS/nixpkgs/blob/master/maintainers/maintainer-list.nix) allows you to provide contact means other than GitHub. The lack of other notification logic already leads exclusionist efforts on the policy side: NixOS/nixpkgs#273220

How about adding Matrix notifications to ofborg? This would fit well into the otherwise heterogeneous ecosystem that already bridges between GitHub and Discourse. Libraries like matrix-commander can provide robust automation for Matrix communication. I might evolve this into a PR once I have a working ofborg test setup.

This would also partially resolve #651

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/setting-up-an-ofborg-instance/36713/1