Fix tapdance when one-shot is disabled.

Update config.h boilerplate to use `#pragma once`

According to @fredizzimo, this is a safer and easier way to handle the
boilerplate.

Add Userspace mention

@drashna mentioned it'd be good to have a mention of the userspace in
the QMK structure section. Rather than rewrite the docs on userspace, I
chose to link to the existing documentation.

Reword the `config.h` section

This section didn't include the possibility of a user `config.h`, and it
wasn't clear exactly how the settings override works.

Update docs: `Makefile` -> `rules.mk`

I think this was a typo, or perhaps an older way to handle it.

Add I2C slave library

- Add I2C slave library for general use.

Added M10-B implementation

Added pin C6 to hardware PWM backlight

AJP10304 Atreus 50 layout (#3403)

UK78 Refactor: rename LAYOUT to LAYOUT_all (#3405)

UK78 refactor and Configurator support (#3395)

* Matrix update

* Keymap refactor

* Configurator support

* Readme cleanup

callum keymap updates (#3402)

* change window focus shortcuts

* hangul

* macos goodness

* re-arrange tab keys

* remove tab switching keys

* left hand func

* glorious macro pad

* workspace rotation keys

* tabbing hotkeys

mitosis:datagrok layout and readme improvements (#3400)

* mitosis:datagrok: improved tenkey layout; changelog + more in README

* mitosis:datagrok enable audio!

* mitosis:datagrok: underscore on right shift, rearrange some symbols

* mitosis:datagrok: add more descriptions to readme

* mitosis:datagrok: abuse space cadet to get equivalent of RSFT_T(KC_UNDS)

Add A Planck keymap with easier shifts and nav (#3399)

keymap BFO9000 built as 6x18 (#3398)

Configurator does not work with melody96 leds (#3396)

* move out led code from keymap.c to melody96.c

* remove the other led_set_user

Fix redox with DIODE_DIRECTION == ROW2COL (#3394)

The code for the redox keyboard was missing
an appropriate #ifdef in the matrix_init
function for the case where DIODE_DIRECTION == ROW2COL

Docs: add resources for git (#3390)

* add resources for git

* add more resources

Added E6v2 keymap & some minor changes (#3392)

* Changed HHKB ALT to GUI etc.

* Swapped DZ60 GUI and ALT key

* Added E6v2 keymap

* Fixed CAPS to LCTL on E6v2

Tada68: Updated links to external sites. (#3389)

Friend was having trouble with their tada since their build environment wasn’t setup.  Updated so they could access the links that were listed (old links 404’d)