Add lighting behavior docs

docs/docs/behavior/lighting.md

@@ -0,0 +1,50 @@
+---
+title: Lighting
+---
+
+## Summary
+
+Lighting is often used for either aesthetics or for the practical purposes of lighting up keys in the dark. 
+Currently ZMK supports RGB underglow, which can be changed and configured using its behavior.
+
+## RGB Action Defines
+
+RGB actions defines are provided through the [`dt-bindings/zmk/rgb.h`](https://github.com/zmkfirmware/zmk/blob/main/app/include/dt-bindings/zmk/rgb.h) header, 
+which is added at the top of the keymap file:
+
+```
+#include <dt-bindings/zmk/rgb.h>
+```
+
+This will allow you to reference the actions defined in this header such as `RGB_TOG`.
+
+Here is a table describing the action for each define:
+
+| Define    | Action                                                    |
+|-----------|-----------------------------------------------------------|
+| `RGB_TOG` | Toggles the RGB feature on and off                        |
+| `RGB_HUI` | Increases the hue of the RGB feature                      |
+| `RGB_HUD` | Decreases the hue of the RGB feature                      |
+| `RGB_SAI` | Increases the saturation of the RGB feature               |
+| `RGB_SAD` | Decreases the saturation of the RGB feature               |
+| `RGB_BRI` | Increases the brightness of the RGB feature               |
+| `RGB_BRD` | Decreases the brightness of the RGB feature               |
+| `RGB_SPI` | Increases the speed of the RGB feature effect's animation |
+| `RGB_SPD` | Decreases the speed of the RGB feature effect's animation |
+| `RGB_EFF` | Cycles the RGB feature's effect forwards                  |
+| `RGB_EFR` | Cycles the RGB feature's effect reverse                   |
+
+## RGB Underglow
+
+The "RGB underglow" behavior completes an RGB action given on press.
+
+### Behavior Binding
+
+- Reference: `&rgb_ug`
+- Parameter: The RGB action define, e.g. `RGB_TOG` or `RGB_BRI`
+
+Example:
+
+```
+&rgb_ug RGB_TOG
+```

docs/sidebars.js

@@ -7,7 +7,11 @@ module.exports = {
       "feature/encoders",
       "feature/underglow",
     ],
-    Behaviors: ["behavior/key-press", "behavior/layers"],
+    Behaviors: [
+      "behavior/key-press",
+      "behavior/layers",
+      "behavior/lighting",
+    ],
     Development: [
       "dev-clean-room",
       "dev-setup",