refactor: Add addClass and removeClass methods to blockSvg (#8337)

* refactor: Add `addClass` and `removeClass` methods to blockSvg

* fix: lint

* fix: jsdoc

core/block_svg.ts

@@ -671,6 +671,24 @@ export class BlockSvg
     }
   }
 
+  /**
+   * Add a CSS class to the SVG group of this block.
+   *
+   * @param className
+   */
+  addClass(className: string) {
+    dom.addClass(this.svgGroup_, className);
+  }
+
+  /**
+   * Remove a CSS class from the SVG group of this block.
+   *
+   * @param className
+   */
+  removeClass(className: string) {
+    dom.removeClass(this.svgGroup_, className);
+  }
+
   /**
    * Recursively adds or removes the dragging class to this node and its
    * children.
@@ -683,10 +701,10 @@ export class BlockSvg
     if (adding) {
       this.translation = '';
       common.draggingConnections.push(...this.getConnections_(true));
-      dom.addClass(this.svgGroup_, 'blocklyDragging');
+      this.addClass('blocklyDragging');
     } else {
       common.draggingConnections.length = 0;
-      dom.removeClass(this.svgGroup_, 'blocklyDragging');
+      this.removeClass('blocklyDragging');
     }
     // Recurse through all blocks attached under this one.
     for (let i = 0; i < this.childBlocks_.length; i++) {