Implement add on selected container

src/Components/SVG/Elements/Container.tsx

@@ -35,4 +35,16 @@ export class Container extends React.Component<IContainerProps> {
       </g>
     );
   }
+
+  public static getDepth(container: Container): number {
+    let depth = 0;
+
+    let current: Container | null = container.props.parent;
+    while (current != null) {
+      depth++;
+      current = current.props.parent;
+    }
+
+    return depth;
+  }
 }