Add Calypso status check (#92902)

.github/workflows/is-calypso-channel-green.yml

@@ -0,0 +1,23 @@
+name: Is Calypso Channel Green?
+run-name: ${{ github.actor }} Checking Calypso Slack Channel Status
+
+on:
+  merge_group:
+
+jobs:
+  check-channel-status:
+    runs-on: ubuntu-latest
+    steps:
+      - run: |
+          STATUS=$(curl -s https://public-api.wordpress.com/wpcom/v2/calypso-slack-channel-status --header "Authorization: ${{ secrets.CALYPSO_CHANNEL_STATUS_API_SECRET }}" | xargs)
+          if [ "$STATUS" = "GREEN" ]; then
+            echo "Calypso Slack channel is green."
+            exit 0
+          elif [ "$STATUS" = "RED" ]; then
+            echo "Calypso Slack channel is red."
+            exit 1
+          else
+            echo "Calypso Slack channel status is unknown."
+            exit 1
+          fi
+        shell: bash