Add profile "GUI"

Follow-up to #28 - and inspired by https://github.com/JabRef/jabref/pull/14950#issuecomment-3824180986

JabRef has three different kind of apps:

- cli: JabKit
- server: JabLS (language server) and JabServ (HTTP server)
- GUI: JabRef GUI

I think, for the latter, there also should be a profile, even though it may be NOOP.

Google found

- https://learn.microsoft.com/en-us/azure/developer/java/containers/overview#understand-jvm-default-ergonomics
- https://developers.redhat.com/articles/2021/11/02/how-choose-best-java-garbage-collector#
- https://gceasy.io/ (linked from https://dzone.com/articles/usestringdeduplication)

I think, I will configure JabRef's Gc for myselve, but I think, completeness for the profiles would be good.

Read issue #28 and the referenced pull request comment first, then inspect how the existing JabKit, JabLS, and JabServ profiles are represented. Done means a GUI profile exists alongside those profiles, with its intended no-op behavior confirmed if applicable.

Written by the indexing model from the issue text.