Systray: About link

[lars18th]

Hi @mpotthoff ,

As it's possible that the new version with GUI will start to be used a lot for new users, I recommend that you include a Menu Entry with an ABOUT window with a link to the project homepage.

You agree?

[ponchofiesta]

This window could also contain some status infos of this instance (sock path, wsl/win, ...).

[benpye]

I would happily review a PR with this change.