[mirotalksfu] - whiteboard :: add eraser

public/Room.html

@@ -199,6 +199,7 @@ access to use this app.
                     <button id="whiteboardRectBtn" class="far fa-square"></button>
                     <button id="whiteboardCircleBtn" class="far fa-circle"></button>
                     <button id="whiteboardSaveBtn" class="fas fa-save"></button>
+                    <button id="whiteboardEraserBtn" class="fas fa-eraser"></button>
                     <button id="whiteboardCleanBtn" class="fas fa-trash"></button>
                     <button id="whiteboardCloseBtn" class="fas fa-times"></button>
                 </div>