Add an option to fill the widget in the panels

[BelkaDev]

Logic was fixed and it should be working as expected now

[fhp]

It works perfectly! Thanks :grin:

[Zren]

I'll probably add a visible: plasmoid.location == PlasmaCore.Types.Floating to the config gui.

I'll also probably change the config label text to "Show popup contents inside panel".

Both can be done after merging though.