Internal and external links are not distinguished

Reproduction steps

1. edit a page with blocknote
2. add two links: one internal, one external
3. observe if there is a visual clue for the external link
4. save
5. observe if there is a visual clue for the external link in view mode

Expected

In the 3 and 5, a visual clue indicates the external link

Actual

In the 3 and 5 the visual clue is missing

Status

Waiting for an answer on https://github.com/TypeCellOS/BlockNote/issues/1118#issuecomment-2996720750

Analysis

In edit mode, this is because it was never introduced in Blocknote.
In view mode, this is because the markdown render indicates only a class on internal link, while the css class wikiexternallink is expected on external link (the style already exists).

<p>
    <span class="wikilink"><a href="http://localhost:15680/xwiki/bin/view/Sandbox/TestPage2">internal link</a></span>
</p>
<p>
    <span class="wikiexternallink"><a href="https://mleduc.xyz">external link</a></span>
</p>