A-Frame plugin: tweaks to the docs

docs/api/plugin-aframe.md

@@ -211,12 +211,10 @@ The `<ar-sources>` primitive is used to specify the [sources of data](./source.m
 ...
 
 <!-- External assets -->
-<a-assets>
-    <video id="my-video" hidden muted loop playsinline autoplay>
-        <source src="my-video.webm" type="video/webm" />
-        <source src="my-video.mp4" type="video/mp4" />
-    </video>
-</a-assets>
+<video id="my-video" hidden muted loop playsinline autoplay>
+    <source src="my-video.webm" type="video/webm" />
+    <source src="my-video.mp4" type="video/mp4" />
+</video>
 ```
 
 ### ar-canvas-source
@@ -334,7 +332,8 @@ AFRAME.registerComponent('my-component', {
 
     tick()
     {
-        const ar = this.ar;
+        const scene = this.el.sceneEl;
+        const ar = scene.systems.ar;
         const session = ar.session;
 
         // ...
@@ -342,11 +341,6 @@ AFRAME.registerComponent('my-component', {
 
     // ...
 
-    get ar()
-    {
-        return this.el.sceneEl.systems.ar;
-    }
-
 });
 ```
 
@@ -460,4 +454,4 @@ The `ar-started` event is emitted when the main loop of the AR scene is set up,
 
 **Details**
 
-* `ar: object`. A reference to the [ar](#ar) system.
+* `ar: object`. A reference to the [ar](#ar) system.