Keyboard: AMJ96 Refactor and Configurator update (#3707)

Keyboard: AMJ96 Refactor and  Configurator update  (#3707)

* AMJ96 Refactor

LAYOUT matrix and default keymap refactored to use full-length keycodes (instead of shorthand).

* Configurator update

Minor physical layout update and made the labels more sensible.

* Readme update

White space correction.

* Default keymap update: #include QMK_KEYBOARD_H

* rules.mk update

Disabled the following options as my local test compile's .hex ended up too big to fit in the available flash space:

MOUSEKEY_ENABLE
EXTRAKEY_ENABLE
BACKLIGHT_ENABLE
RGBLIGHT_ENABLE

If this is undesirable, suggestions are welcome.

* Config/rules update

Re-enabled MOUSEKEY_ENABLE, EXTRAKEY_ENABLE, BACKLIGHT_ENABLE, and RGBLIGHT_ENABLE and disabled COMMAND_ENABLE in rules.mk; enabled NO_ACTION_MACRO and NO_ACTION_FUNCTION per @drashna

* Swapped `___` for `XXX` in amj96.h per @mechmerlin