Update libraries.json from CI (#80)

Co-authored-by: libhal-bot <libhal-bot@users.noreply.github.com>

Author: github-actions[bot]

libraries.json

@@ -28,6 +28,10 @@
         "version": "4.20.0",
         "url": "https://libhal.github.io/api/libhal/4.20.0"
       },
+      {
+        "version": "4.21.0",
+        "url": "https://libhal.github.io/api/libhal/4.21.0"
+      },
       {
         "version": "main",
         "url": "https://libhal.github.io/api/libhal/main"