Add permissive hold functionality to input

I’ve noticed some pretty weird interactions when using home row mods on my xyz board that make it pretty unusable for me right now unfortunately. I have shift mapped to a multiaction on ‘d’ when i hold it, but if i type ‘da’ and press a down before i release the d key, it will send ‘ad’. At a very minimum, i think the default functionality here would be to send ‘da’ if both keystrokes happen within the tapping term, but even more useful functionality would be permissive hold, which would respect the hold multiaction even if it all happens within the tapping term, as long as the ‘a’ keystroke down and ‘a’ keystroke up all happen while ‘d’ is held down.

a more in depth breakdown of this behavior can be found here

https://docs.qmk.fm/tap_hold, but i haven’t found a way to make a 40% board usable at any real speed without having some parity with this feature