Adding documentation about CI/CD and .gitignoring MkDocs build

.gitignore

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+/site/

docs/mkdocs/forgejo-ci.md

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+# CI/CD
+
+!!! TODO
+	This documentation might not be complete
+
+``` console
+Install required stuff and things on Debian based system
+$ sudo apt-get install rsync
+Make a user to have limited access
+$ sudo useradd adduser --home /varasto/verkkojuuri --system verkkojuuri --shell /bin/sh
+$ cd /varasto/verkkojuuri
+$ sudo -u verkkojuuri ssh-keygen
+$ sudo -u verkkojuuri cat .ssh/id_rsa
+copy the result to your Forgejo as an action secret ssh_private_key
+$ sudo -u verkkojuuri cat .ssh/id_rsa.pub
+copy the result to your Forgejo as an action variable ssh_public_key 
+$ sudo -u verkkojuuri ssh-keygen -p
+enter new password to protect the private key or delete it
+or something security blah blah... No really, assume this is accessed!
+(you just did and you are not verkkojuuri so think about it)
+sudo -u verkkojuuri cp .ssh/id_rsa.pub .ssh/authorized_keys
+this let's us trust the key
+$ sudo usermod -aG ssh verkkojuuri
+give us permission to get connected via ssh (might not be needed)
+```
+
+!!! WARNING
+	You might want to check out `rssh`, `scponly` or similar
+	more restricted shell to use with the account.
+	
+	Change it afterwards using `sudo usermod -s /Sbin/HELL verkkojuuri`
+
+Then you just like build and like rsync the files
+using a forgejo action runner passing it the relevant
+secrets. In practise you'll make it execute
+
+``` console
+$ mkdocs build
+$ rsync -e "ssh -rclthv --exclude --delete-after .git site/ verkkojuuri@jakest.us:site
+```
+	
+
+
+And well yeah serve them files with Apache or whatever.
+That's out of the scope of this document.
+
+## Credits
+Thank you Nexy and Tulir for your help!
+
+- Nexy's blogpost: [https://blog.nexy7574.co.uk/2025/01/22/new-infrastructure/](https://blog.nexy7574.co.uk/2025/01/22/new-infrastructure/)
+- Tulir's relevant stuff:
+	- [https://github.com/maunium/mau.fi/blob/main/.gitlab-ci.yml](https://github.com/maunium/mau.fi/blob/main/.gitlab-ci.yml)
+	- [https://github.com/mautrix/docs/blob/master/.gitlab-ci.yml](https://github.com/mautrix/docs/blob/master/.gitlab-ci.yml)