[Keymap] update: add extrakey support for macOS media keys (#5263)

* add dusty keymap

* change keymap folder to match my github username

* initial keymap completed in comments only

* layout without NAV completed in comments only

* disable Command to prevent interference with Space Cadet keys

* switch _ and \ in the symbol layer

* Layers complete through _NAV

* add thumb keys to _NAV

* complete _NUM

* all layouts complete; still needs `process_user_record()`

* completed first draft of keymap; still needs config.h to match

* corrected keycodes for Mac macro-volume keys

* fix Mac mute keycode

* add missing Mac keycodes for previous and next track

* placeholder for qwerty layout, not yet completed;

remove unnecessary breaks;

add todos

* eliminate Preonic branch before switching to Minidox branch:

• delete dustypomerleau Preonic keymap folder

• complete keymap.c (QWERTY layer, vanilla numbers layer)

TODO:
• add preferences to config.h
• complete the README

* edit commented keymap diagrams for clarity in dual function keys

* define initial config.h and add rules.mk for mouse key support

* fix redundant line after implementation of tap_code()

* fixed key_timer declaration, added README and rules

* formatting of keymap

* add CTPC to config

* cycle thumb keys to favor center position

* modify config.h for temporary Pro Micro compatibility

* remove superfluous call to use serial; homebrewed mod tap keys are still broken with OSL

* merge _SYS and _MEDIA on new Z_SYS key

* ALT_OP example of new MT macro complete

* initial narze-inspired MT fixes in PRU

* add (currently superfluous) custom keycode for the _SYS layer

* rudimentary `OSL` symbol macros that immediately register the mod and fail to reset the oneshot layer, but do output the proper keys—fix both of these things

* remove permissive hold to improve tapping performance

* remove calls to `clear_oneshot_layer_state()`, as they have no effect inside `process_record_user()`. Tapdance appears to be the way forward.

* final commit before tapdance code; correct layout in comments

* initial tapdance code for shifted mod taps

* add numeric and ergo NUM layers and pinky shifts for keycuts

* add TD() wrappers to tapdance codes and clean up commented layout guides

* add faux return to cur_dance to allow compilation - TODO: research what the default clause should be in cur_dance

* update commented schematics for better readability

* add backspace and delete to lockable layers, Z_SYS -> SYS_Z for consistency, fix schematic errors

* add `DOUBLE_SINGLE_TAP` to tapdance cases to allow doubling of the single tap character without waiting tapping term

* remove reduced oneshot tapping toggles

* update README

* newline tweak :)

* Update keyboards/minidox/keymaps/dustypomerleau/keymap.c

Co-Authored-By: dustypomerleau <dustypomerleau@users.noreply.github.com>

* Update keyboards/minidox/keymaps/dustypomerleau/config.h

Co-Authored-By: dustypomerleau <dustypomerleau@users.noreply.github.com>

* Update keyboards/minidox/keymaps/dustypomerleau/config.h

Co-Authored-By: dustypomerleau <dustypomerleau@users.noreply.github.com>

* Update keyboards/minidox/keymaps/dustypomerleau/config.h

Co-Authored-By: dustypomerleau <dustypomerleau@users.noreply.github.com>

* Update keyboards/minidox/keymaps/dustypomerleau/config.h

Co-Authored-By: dustypomerleau <dustypomerleau@users.noreply.github.com>

* remove `PREVENT_STUCK_MODIFIERS`, as this is default behavior

* enable extrakey in rules to enable media keys

* enable extrakeys for media key compatibility on macOS

* add dash and slash to _NUM layers

* change to universal volume keycodes

* revert micro volume adjustments to macOS-specific codes due to lack of functionality (macro volume adjustments are still universal)