Full licensing information missing

[wojnilowicz]

The workrave is released under the GPL-3.0-or-later license. Other licenses:

1. libs/config/include/config/IConfiguratorListener.hh: GPL-2.0-or-later
2. ui/app/toolkits/gtkmm/platforms/unix/gtktrayicon.{c,h}: LGPL-2.1-or-later
3. ui/app/toolkits/gtkmm/platforms/unix/protocols/wlr-layer-shell-unstable-v1.xml: HPND

The issue is that on the main page only GPL-3.0-or-later is listed and the repo contains only its text as seen at https://github.com/rcaelers/workrave/blob/main/COPYING

Shouldn't the repo list other licenses and their texts as well?

The issue has been discovered during the analysis at https://bugzilla.redhat.com/show_bug.cgi?id=2351398

[rcaelers]

I fixed IConfiguratorListener.hh; this file was not properly converted to GPL-3 because of some typos in the license text.

I added LICENSES.md with a license overview. I will also update the credits in the "about" window.