Use Unicode symbol for X

Author: gtca

layouts/partials/main/cover.html

@@ -29,7 +29,7 @@
         Zulip
       </a>
       <a class="btn btn-light btn-outline-dark btn-twitter" href="https://x.com/scverse_team" target="_blank">
-        X
+        𝕏
       </a>
       <a class="btn btn-light btn-outline-dark btn-bluesky" href="https://bsky.app/profile/scverse.bsky.social" target="_blank">
         Bluesky