feat: add Zulip archive cron workflow

Signed-off-by: Kate Goldenring <[email protected]>

.github/workflows/main.yaml

@@ -0,0 +1,22 @@
+on:
+  schedule:
+    # Run every hour
+   - cron: '0 * * * *'
+
+jobs:
+  publish_archive_job:
+    runs-on: ubuntu-latest
+    name: A job to publish zulip-archive in GitHub pages
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v3
+    - name: Run archive
+      id: archive
+      uses: zulip/zulip-archive@master
+      with:
+        zuliprc: ${{ secrets.ZULIPRC }}
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        # To keep the git history from ballooning, will overwrite the Git
+        # history in the repository, but keep all the content.
+        delete_history: true
+        archive_branch: main