Howto RGB Layers

Very common question, very simple answer.
Comments and suggestions welcome

docs/layers.md

@@ -68,3 +68,26 @@ keyboard.keymap = [
 	],
 ]
 ```
+
+## Advanced Example
+A common question is: "How do I change RGB background based on my active layer?"
+Here is _one_ (simple) way of many to go about it.
+
+```python
+from kmk.modules.layers import Layers as _Layers
+from kmk.extensions.rgb import RGB
+
+rgb = RGB(...) # your RGB configuration goes here
+keyboard.extensions.append(rgb)
+
+class Layers(_Layers):
+	last_top_layer = 0
+	hues = (4, 20, 69)
+	
+	def after_hid_send(keyboard):
+		if keyboard.active_layers[0] != self.last_top_layer:
+			self.last_top_layer = keyboard.active_layers[0]
+			rgb.set_hsv_fill(self.hues[self.last_top_layer], 255, 255)
+
+keyboard.modules.append(Layers())
+```