Make keybindings more flexible

[RobertMueller2]

So far, 1..10 was easy to bind programmatically, because it can be done in a for loop.

Allowing additional keys makes the tool more flexible, but also adds complexity.

Ideas:

• the switches could allow a tokenized list of hotkeys, say, --switch-desktop-modifiers CTRL,WIN+0%CTRL,WIN+1
• it could be possible to specify switches more than once and each would start binding at 0
• "NUMBERS" could be used as an alias for 1..10
• "FKEY" could be used as an alias for F1..F12

For much later, perhaps a followup issue:

• "KP_NUM" could be used as an alias for KP0 through KP9
• "KP_NAV" could be used as an alias for KP_INS through KP_PgUp

These last two are trickier. Windows virtual keycodes don't distinguish keypad directions (e.g. Ins) from a regular Ins. It's probably possible to distinguish them via scancode (https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-kbdllhookstruct), but Win32HotkeyListener's architecture doesn't support this at this point. It would have to allow sub-actions for the same hotkey.

[RobertMueller2]

Overlaps with #4