Update CI workflow to include mkdocs-autorefs in dependencies

Author: JonneSaloranta

.github/workflows/ci.yaml

@@ -18,5 +18,5 @@ jobs:
         with:
           key: ${{ github.ref }}
           path: .cache
-      - run: pip install mkdocs-material
+      - run: pip install mkdocs-material mkdocs-autorefs
       - run: mkdocs gh-deploy --force