(ui): add check/uncheck slot in SSignalButton
Description
SSignalButton is a checkable button that emits signals when the button is clicked and toggled.
Only the slot setChecked(bool)
is currently available, but it can be useful to add check
/uncheck
slots to help us to manage the button state without using a boolean signal.
Proposal
Update the editor to add the two slots.
Don't forget to update the doxygen: old impl
attribute is still used.