fix: extend highlighting to headings, strong, em, blockquote

UNHCR docs use #### prefixes extensively, rendering text as h4 elements
which were not in highlightComponents. Dataset mentions inside headings
or bold text were invisible.

app/components/MarkdownAnnotator.js

@@ -129,6 +129,15 @@ export default function MarkdownAnnotator({ selectedDocIndex, selectedPage, curr
         li: highlightWrapper('li'),
         td: highlightWrapper('td'),
         th: highlightWrapper('th'),
+        h1: highlightWrapper('h1'),
+        h2: highlightWrapper('h2'),
+        h3: highlightWrapper('h3'),
+        h4: highlightWrapper('h4'),
+        h5: highlightWrapper('h5'),
+        h6: highlightWrapper('h6'),
+        blockquote: highlightWrapper('blockquote'),
+        strong: highlightWrapper('strong'),
+        em: highlightWrapper('em'),
     };
 
     return (