mostly finished rewrite

public/node_modules/dom-helpers/esm/addClass.d.ts

@@ -0,0 +1,7 @@
+/**
+ * Adds a CSS class to a given element.
+ *
+ * @param element the element
+ * @param className the CSS class name
+ */
+export default function addClass(element: Element | SVGElement, className: string): void;