Add custom services #1483
Description
Add an option to add your own custom service - basically an icon on the main menu that redirects the user to another place, either within the network (local ipv4), or a domain name that correctly points to the right place
Use case: If you want to host an app outside of Umbrel (for security or incompatibility reasons), then you can have a pretty link towards your service. Bonus points if it automatically logs in to said service.