[mirotalksfu] - whiteboard :: add bg color set

public/Room.html

@@ -151,6 +151,10 @@ access to use this app.
                         <br />
                         <input id="wbDrawingColorEl" type="color" value="#FFFFFF" />
                         <br />
+                        <i class="fas fa-palette"></i> Background color
+                        <br />
+                        <input id="wbBackgroundColorEl" type="color" value="#000000" />
+                        <br />
                     </div>
                 </div>
             </div>