purge old action artifacts nightly

[skip ci]

.github/workflows/purge-artifacts.yml

@@ -0,0 +1,14 @@
+name: Purge old artifacts
+
+on:
+  schedule:
+  - cron: '0 9 * * *'   # every day at 9 AM UTC = 5 AM EDT
+
+jobs:
+  purge-artifacts:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: kolpav/purge-artifacts-action@v1
+      with:
+        token: ${{ secrets.GITHUB_TOKEN }}
+        expire-in: 0