[Keymap] add "ridingqwerty" user and keymap for atreus keyboard (#6533)

* add userspace and atreus keymap

* cleaning up notes/comments

* Update keyboards/atreus/keymaps/ridingqwerty/atreus.c

Co-Authored-By: Joel Challis <git@zvecr.com>

* Update keyboards/atreus/keymaps/ridingqwerty/atreus.c

Co-Authored-By: Joel Challis <git@zvecr.com>

* Create readme.md

* remove reference to matrix_init_kb from atreus.c

* correct atreus.c

* remove unnecessary defines

* merge register/unregister sequence into single tapcode

* move 'LAYOUT to keymap.c; remove atreus.h

* remove TAPPING_TERM from keyboard-level config.h

users/ridingqwerty/ridingqwerty.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include "quantum.h"
+#include "process_records.h"
+
+enum userspace_layers
+{
+    _QWERTY = 0,
+    _EDITOR,
+    _NUMBER,
+    _SYMBOL,
+    _F_KEYS,
+    _DEBUG,
+    _SECRET,
+    _FINAL
+};
+
+// modtaps
+#define LS_Z MT(MOD_LSFT, KC_Z)
+#define LC_ESC MT(MOD_LCTL, KC_ESC)
+#define LG_TAB MT(MOD_LGUI, KC_TAB)
+#define LA_LBRC MT(MOD_LALT, KC_LBRC)
+#define LS_RBRC MT(MOD_LSFT, KC_RBRC)
+#define RS_MINS MT(MOD_RSFT, KC_MINS)
+#define RA_EQL MT(MOD_RALT, KC_EQL)
+//RG_LMOT defined in process_records.h
+#define RC_ENT MT(MOD_RCTL, KC_ENT)
+#define RS_SLSH MT(MOD_RSFT, KC_SLSH)
+// layertaps
+#define ED_A LT(_EDITOR, KC_A)
+#define ED_ESC LT(_EDITOR, KC_ESC)
+#define NM_SCLN LT(_NUMBER, KC_SCLN)
+#define NM_BSPC LT(_NUMBER, KC_BSPC)
+#define SM_SPC LT(_SYMBOL, KC_SPC)
+#define SC_TAB LT(_SECRET, KC_TAB)
+#define FK_DOT LT(_F_KEYS, KC_DOT)
+