license this repo under the MIT license

All previous contributors are asked to sign off on licensing this repo
under the MIT license in PR 12
(#12). Once all
contributors signed-off, this commit will be merged into the main
branch and this repo will be licensed under the MIT license.

Don't track copyright years in the license, as that is cumbersome and
also not done in other projects anymore:
https://daniel.haxx.se/blog/2023/01/08/copyright-without-years/
https://github.com/rails/rails/pull/47467

MIT License:
https://opensource.org/license/MIT
https://choosealicense.com/licenses/mit/

README.md

@@ -73,3 +73,7 @@ Build a new NixOS Proxmox VE Template for the chaosknoten:
 ```shell
 nix build .#proxmox-chaosknoten-nixos-template
 ```
+
+## License
+
+This CCCHH nix-infra repository is licensed under the [MIT License](./LICENSE).