Keyup events should (optionally?) be ignored

[luke-jr]

When I:

• Press Esc to close another window, leaving scrcpy in focus
• Ctrl-Alt-E to switch to the virtual desktop with scrcpy in focus

(or anything like that...)

scrcpy forwards the key-up event for the key to the phone, and Android apps close (Esc) or enter an 'e' character

At least an option should be available (if not default behaviour) to ignore key-up events that don't match a previous key-down.

(It may also make sense to send key-up when focus is lost, for any keys which had been down?)