[Docs] Add examples to RGB Matrix Indicators docs (qmk#12797)

Author: drashna

docs/feature_rgb_matrix.md

@@ -741,3 +741,42 @@ void rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
     }
 }
 ```
+
+#### Examples :id=indicator-examples
+
+This example sets the modifiers to be a specific color based on the layer state.  You can use a switch case here, instead, if you would like.  This uses HSV and then converts to RGB, because this allows the brightness to be limited (important when using the WS2812 driver).
+
+```c
+void rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
+    HSV hsv = {0, 255, 255};
+    
+    if (layer_state_is(layer_state, 2)) {
+        hsv = {130, 255, 255};
+    } else {
+        hsv = {30, 255, 255};
+    }
+    
+    if (hsv.v > rgb_matrix_get_val()) {
+        hsv.v = rgb_matrix_get_val();
+    }
+    RGB rgb = hsv_to_rgb(hsv);
+    
+    for (uint8_t i = led_min; i <= led_max; i++) {
+        if (HAS_FLAGS(g_led_config.flags[i], 0x01)) { // 0x01 == LED_FLAG_MODIFIER
+            rgb_matrix_set_color(i, rgb.r, rgb.g, rgb.b);
+        }
+    }
+}
+```
+
+If you want to indicate a Host LED status (caps lock, num lock, etc), you can use something like this to light up the caps lock key: 
+
+```c
+void rgb_matrix_indicators_advanced_user(uint8_t led_min, uint8_t led_max) {
+    if (host_keyboard_led_state().caps_lock) {
+        RGB_MATRIX_INDICATOR_SET_COLOR(5, 255, 255, 255); // assuming caps lock is at led #5
+    } else {
+        RGB_MATRIX_INDICATOR_SET_COLOR(5, 0, 0, 0);
+    }
+}
+```