Depend on standard KDE/Qt snap instead on your own

[LaurentBonnaud]

Hi,

first thank you for providing this software and making it available as a snap!

The plumber snap depends on the qt515-core20 snap, that you also created:

$ snap connections plumber
Interface              Plug                     Slot                            Notes
[...]
content[qt515-core20]  plumber:qt515-core20     qt515-core20:qt515-core20       -

The problem with that is the disk space it uses.
How about depending on the kde-frameworks-5-102-qt-5-15-8-core22-sdk snap instead?
This "standard" snap is probably already installed on the systems of people who already use KDE software as snaps.