Update needle-engine attributes

documentation/reference/needle-engine-attributes.md

@@ -13,7 +13,9 @@ The table below shows a list of the most important ones:
 | `dracoDecoderType` | draco decoder type. Options are `wasm` or `js`. See [three.js documentation](https://threejs.org/docs/#examples/en/loaders/DRACOLoader.setDecoderConfig) |
 | `ktx2DecoderPath` | URL to the KTX2 decoder |
 | **Rendering** | |
-| `skybox-image` | optional, URL to a skybox image (background image) or a preset string: `studio`, `blurred-skybox`, `quicklook`, `quicklook-ar` | 
+| `background-color` | optional, hex color to be used as a background color. Examples: `rgb(255, 200, 100)`, `#dddd00` | 
+| `background-image` | optional, URL to a skybox image (background image) or a preset string: `studio`, `blurred-skybox`, `quicklook`, `quicklook-ar` | 
+| `background-blurriness` | optional, bluriness value between 0 (no blur) and 1 (max blur) for the `background-image`. Example: `background-blurriness="0.5"` | 
 | `environment-image` | optional, URL to a environment image (environment light) or a preset string: `studio`, `blurred-skybox`, `quicklook`, `quicklook-ar` |
 | `contactshadows` | optional, render contact shadows |
 | `tone-mapping` | optional, supported values are `none`, `linear`, `neutral`, `agx` |