Add automatic workflow build artifact cleanup.

.github/workflows/nightly_cleanup.yml

@@ -0,0 +1,13 @@
+name: 'nightly artifacts cleanup'
+on:
+  schedule:
+    - cron: '0 1 * * *' # every night at 1 am UTC
+
+jobs:
+  delete-artifacts:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: kolpav/purge-artifacts-action@v1
+        with:
+          token: $
+          expire-in: 7days # Set this to 0 to delete all artifacts