[olivetin] add a guide for OliveTin

[kimdiallo]

Looks good and fits well.

https://github.com/OliveTin/OliveTin

https://www.olivetin.app

[EV21]

As of my knowledge this app does currently not have an own authentification system. So when you directly give access to this app via the web backend anyone (who knows the domain) can run your configured commands.

• Maybe an auth proxy (see #1115) could be a solution for this. 🚀
• You can also use a ssh tunnel to securely access the internal port if this is only a one person show.
  e.g. ssh -L 8042:0.0.0.0:1337 [email protected] -> http://localhost:8042 to have this persistent you may need something like autossh and a ssh config file on your local computer