Add notes about unsupported QPA plugins


Some QPA plugins are unmaintained and may pose risks if someone
uses them in an uncontrolled environment. They are currently quite
underdocumented, but mentioned in the overview page for QPA.
Make it explicit there that they are considered experimental.

Pick-to: 6.8 6.12
Change-Id: Iffb3554b0a5bbbc3f13d31dc6849c0dc73e0437f
Reviewed-by: Vladimir Minenko <vladimir.minenko@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
commit0763069d996bc1cf21a4486fb0a49636752ab253
parent051b0b0980f328af3aee86e495d0d29a37028891
authorEskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
committerEskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
commit timeWed, 7 Oct 2026 12:22:40 +0000