Support mapping Control key modifier combination

[XuYicong]

Implements #124

Managed to implement this without breaking keymap format compatibility, by prepending a ⌃ symbol before the key name to mark it a modifier combination.

As Control key is now used as a modifier key, it can't be mapped separately any more. But existing keymaps with Control key mapped can still use it.

Limitations

Can only map Button type actions, this excludes DraggableButton and Joystick. It's because these two mainly rely on key code (instead of key name) to distinguish different keys. It's further because of the underlying keymap format, in which there are not enough fields for key name for these types.

[TheMoonThatRises]

This could be the MacOS beta, but when using a keymapping with a control prefix, it makes the error sound (this also happens with cmd+k).

[Depal1]

This could be the MacOS beta, but when using a keymapping with a control prefix, it makes the error sound (this also happens with cmd+k).

I couldn't replicate this in macOS Sonoma, neither for the cmd+k. It might be a beta issue as you have suggested or shortcut conflicts in your environment.