Add example for turning off RGB colors and retaining indicator function (#14997)

* Add init function for solid effect with colors off

* Restructure sentence

Co-authored-by: filterpaper <filterpaper@localhost>

docs/feature_rgb_matrix.md

@@ -780,3 +780,13 @@ void rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
     }
 }
 ```
+
+#### Indicators without RGB Matrix Effect
+
+If you want to just use RGB indicators without RGB matrix effect, it is not possible to disable the latter because toggling RGB off will disable everything. You can workaround it with solid effect and colors off using this init function:
+```c
+void keyboard_post_init_user(void) {
+    rgb_matrix_mode_noeeprom(RGB_MATRIX_SOLID_COLOR);
+    rgb_matrix_sethsv_noeeprom(HSV_OFF);
+}
+```