Allow for RGB actions to take place on Keydown instead of Keyup (#16886)

* Allow for switch on keydown

* add docs

quantum/process_keycode/process_rgb.c

@@ -52,7 +52,11 @@ static void __attribute__((noinline, unused)) handleKeycodeRGBMode(const uint8_t
  */
 bool process_rgb(const uint16_t keycode, const keyrecord_t *record) {
     // need to trigger on key-up for edge-case issue
+#ifndef RGB_TRIGGER_ON_KEYDOWN
     if (!record->event.pressed) {
+#else
+    if (record->event.pressed) {
+#endif
 #if (defined(RGBLIGHT_ENABLE) && !defined(RGBLIGHT_DISABLE_KEYCODES)) || (defined(RGB_MATRIX_ENABLE) && !defined(RGB_MATRIX_DISABLE_KEYCODES))
         uint8_t shifted = get_mods() & MOD_MASK_SHIFT;
 #endif