Add Data URL as a supported value type for gltf-model component

Author: vincentfretin

docs/components/gltf-model.md

@@ -74,10 +74,11 @@ file.
 
 ## Values
 
-| Type     | Description                          |
-|----------|--------------------------------------|
-| selector | Selector to an `<a-asset-item>`      |
-| string   | `url()`-enclosed path to a glTF file |
+| Type     | Description                                 |
+|----------|---------------------------------------------|
+| selector | Selector to an `<a-asset-item>`             |
+| string   | `url()`-enclosed path to a glTF file        |
+| Data URL | data:application/octet-stream;base64,<data> |
 
 ## Events