Run tests weekly + Slack notification (#347)

* weekly ci tests

* Finish weekly ci tests workflow

Author: lola831

.github/workflows/weekly-ci-tests.yml

@@ -0,0 +1,47 @@
+name: Weekly CI tests
+
+# No permissions needed
+permissions: {}
+
+# Trigger every Thursday at 9:15 AM Pacific Time (16:15 UTC)
+on:
+  schedule:
+    - cron: '15 16 * * 4'
+
+jobs:
+  run-tests:
+    uses: ./.github/workflows/run-tests.yml
+    with:
+      # Use the default branch" (i.e. main)
+      ref: ''
+
+  notify:
+    name: Notify Slack
+    needs: run-tests
+    runs-on: ubuntu-latest
+    if: always()
+    steps:
+        - name: Post result to Slack
+          uses: slackapi/slack-github-action@b0fa283ad8fea605de13dc3f449259339835fc52
+          with:
+            webhook: ${{ secrets.SLACK_WEBHOOK_URL}}
+            webhook-type: incoming-webhook
+            payload: |
+              {
+                "blocks": [
+                    {
+                    "type": "section",
+                    "text": {
+                      "type": "mrkdwn",
+                      "text": "*Weekly CI tests* <${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}|run #${{ github.run_number }}> finished."
+                    }
+                  },
+                  {
+                    "type": "section",
+                    "text": {
+                      "type": "mrkdwn",
+                      "text": "${{ needs.run-tests.result == 'success' && '✅ All tests passed!' || '🚨 Some tests failed!' }}"
+                    }
+                  }
+                ]
+              }