Custom Tapping Term per key (#5009)

* Add customizable tapping terms

* Add Documentation

* Fix function

* Fixes

* It's not a pointer

* Add debugging output

* Update documentation to be at least vaguely accurate

* Use `get_tapping_term(tapping_key.event)` instead

`e` doesn't include column and row information, properly. It registers as 255, regardless of the actual keypress.

However `tapping_key.event` actually gives the correct column and row information.  It appears be the correct structure to use. 

In fact, it looks like the issue is that `e` is actually the "TICK" structure, as defined in keyboard.h

* Use variable tapping term value rather than define

* Silly drashna - tapping_key.event, not event

* add get_event_keycode() function

* Fix typo

Co-Authored-By: drashna <drashna@live.com>

* Remove post_process_record_quantum since it's the wrong PR

* Update quantum/quantum.c

Co-Authored-By: drashna <drashna@live.com>

* Better handle ifdef statement for permissive hold

Since we can't be sure that tapping term is actually 500

* Update quantum.c comments based on feedback

* Clean up get_tapping_term function

Clean up function so that users don't need to call the event function, and instead only check the keycode

* Add ability to run functionality on and off

* Make ifdef's more compact

docs/config_options.md

@@ -126,6 +126,8 @@ If you define these options you will enable the associated feature, which may in
 
 * `#define TAPPING_TERM 200`
   * how long before a tap becomes a hold, if set above 500, a key tapped during the tapping term will turn it into a hold too
+* `#define TAPPING_TERM_PER_KEY`
+  * enables handling for per key `TAPPING_TERM` settings
 * `#define RETRO_TAPPING`
   * tap anyway, even after TAPPING_TERM, if there was no other key interruption between press and release
   * See [Retro Tapping](feature_advanced_keycodes.md#retro-tapping) for details