doc: 更新示例

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Samples/MediaDevice.razor

@@ -37,6 +37,9 @@
 
     <video class="bb-video" muted playsinline autoplay style="height: auto; width: auto;"></video>
 
-    <canvas class="b-video-image"></canvas>
+    <canvas class="bb-video-image"></canvas>
+
+    <div>Image</div>
+    <img class="bb-image" src="" />
 </DemoBlock>