Update actions/upload-pages-artifact action to v4 (#8)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/site.yaml

@@ -19,7 +19,7 @@ jobs:
           chmod -c -R +rX "_site/" | while read line; do
           echo "::warning title=Invalid file permissions automatically fixed::$line"
           done
-      - uses: actions/upload-pages-artifact@v3
+      - uses: actions/upload-pages-artifact@v4
 
   deploy:
     needs: upload-artifact