fix: Filter out headings inside dialogs for toc highlighting (#792)

Headline highlighting was broken for headlines with dialogs.

<img width="2720" height="1394" alt="image"
src="https://github.com/user-attachments/assets/99981148-403d-4c77-af6c-82654eaeb457"
/>

Co-authored-by: Robert Schuster <77234379+therobrob@users.noreply.github.com>

Author: MoritzWeber0

assets/js/highlightHeadline.js

@@ -1,7 +1,7 @@
 function initHighlightHeadline() {
   const headings = Array.from(
     document.querySelectorAll(".o-single__highlight :is(h1, h2, h3)"),
-  );
+  ).filter((heading) => !heading.closest("dialog"));
   const windowPath = window.location.pathname;
   if (headings.length === 0) {
     return;