DEV: Add slug parameter to hashtag-decorator (#27917)

In order to facilitate discourse-tag-icons and discourse-category-icons to render icons for post content, we need to provide an additional slug parameter here

app/assets/javascripts/discourse/app/lib/hashtag-decorator.js

@@ -100,6 +100,7 @@ export function decorateHashtags(element, site) {
         .generateIconHTML({
           icon: site.hashtag_icons[hashtagType],
           id: hashtagEl.dataset.id,
+          slug: hashtagEl.dataset.slug,
         })
         .trim();
       iconPlaceholderEl.replaceWith(domFromString(hashtagIconHTML)[0]);