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

* Allow for switch on keydown

* add docs

docs/feature_rgb_matrix.md

@@ -777,6 +777,7 @@ These are defined in [`color.h`](https://github.com/qmk/qmk_firmware/blob/master
 #define RGB_MATRIX_DISABLE_KEYCODES // disables control of rgb matrix by keycodes (must use code functions to control the feature)
 #define RGB_MATRIX_SPLIT { X, Y } 	// (Optional) For split keyboards, the number of LEDs connected on each half. X = left, Y = Right.
                               		// If RGB_MATRIX_KEYPRESSES or RGB_MATRIX_KEYRELEASES is enabled, you also will want to enable SPLIT_TRANSPORT_MIRROR
+#define RGB_TRIGGER_ON_KEYDOWN      // Triggers RGB keypress events on key down. This makes RGB control feel more responsive. This may cause RGB to not function properly on some boards
 ```
 
 ## EEPROM storage :id=eeprom-storage

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