Update and add aria-labels to icon links

Author: Susan Vanderplas

_quarto.yml

@@ -31,14 +31,17 @@ book:
     style: floating
     collapse-level: 3
   page-footer:
-    left: "Copyright 2024, Susan Vanderplas"
+    left: "Copyright 2025, Susan Vanderplas"
     right:
       - icon: github
         href: "https://github.com/srvanderplas"
-      - icon: twitter
-        href: "https://twitter.com/srvanderplas"
+        aria-label: GitHub
       - icon: mastodon
         href: "https://datavis.social/%40srvanderplas"
+        aria-label: Mastodon
+      - icon: bluesky
+        href: "https://%40srvanderplas.bsky.social"
+        aria-label: Bluesky
   comments:
     giscus:
       repo: srvanderplas/stat-computing-r-python