remove artifacts older than 21 days (#157)

Author: webbertakken

.github/workflows/cleanup.yml

@@ -0,0 +1,13 @@
+name: Delete old artifacts
+on:
+  schedule:
+    - cron: '30 10 * * *' # every day at 10:30
+
+jobs:
+  delete-artifacts:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: kolpav/purge-artifacts-action@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          expire-in: 21 days