[Docs] RGB Matrix Caps Lock and Layer indicator example (qmk#13367)

Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: filterpaper <filterpaper@localhost>

Author: 4 people

docs/feature_rgb_matrix.md

@@ -624,6 +624,39 @@ void rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
 }
 ```
 
+### Indicator Examples :id=indicator-examples
+
+Caps Lock indicator on alphanumeric flagged keys:
+```c
+void rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
+    if (host_keyboard_led_state().caps_lock) {
+        for (uint8_t i = led_min; i <= led_max; i++) {
+            if (g_led_config.flags[i] & LED_FLAG_KEYLIGHT) {
+                rgb_matrix_set_color(i, RGB_RED);
+            }
+        }
+    }
+}
+```
+
+Layer indicator on all flagged keys:
+```c
+void rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
+    for (uint8_t i = led_min; i <= led_max; i++) {
+        switch(get_highest_layer(layer_state|default_layer_state)) {
+            case RAISE:
+                rgb_matrix_set_color(i, RGB_BLUE);
+                break;
+            case LOWER:
+                rgb_matrix_set_color(i, RGB_YELLOW);
+                break;
+            default:
+                break;
+        }
+    }
+}
+```
+
 ### Suspended state :id=suspended-state
 To use the suspend feature, make sure that `#define RGB_DISABLE_WHEN_USB_SUSPENDED true` is added to the `config.h` file.