add support for Caps Word

[jurica]

I added support for Caps Word as explained in https://feedback.vial.today/suggestions/331656/add-caps_word-keycode-to-gui

[xyzz]

Caps word isn't present on protocol v5, it should be removed, and then it's the same issue as in #191 (comment) to hide it in the UI when unsupported

[jurica]

@xyzz thanks for the feedback, I wasn't aware of that.
I thought about a solution for the problem and came around with the following approach: extend Keycode class by a property "min_protocol". This makes it possible to filter out keycodes not supported by the selected keyboard. (This would also allow to extend it further with a property max_protocol if later versions drop a keycode.)

Unfortunately I only got this working here if I put the "Quantum keys" on an own tab only containing these keys.
I'm not sure if this is due to how things get set up in tabbed_keycodes.py or my environment (I'm on macOS on an Apple Silicon machine and was not able to get Python 3.6 and PyQt5 set up, so I upgraded Vial to PyQt6 in order to be able to do some development. But my Qt6 port is not yet fully working.).

Looking forward some feedback on my approach.

[lesshonor]

It's worth nothing that the hex code for Caps Word did exist and function back in "v5" even if it wasn't exposed in the GUI, and there are records of that hex code's use in the Vial discord at least as far back as September 2022.

[philliphall]

Just adding a plus one for this feature :-)