ci: add guardrails workflow [skip deploy] (#28)

Author: cchawn

.github/workflows/guardrails.yaml

@@ -0,0 +1,15 @@
+---
+name: 'Guardrails'
+
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - synchronize
+
+jobs:
+  stale:
+    name: Check Guardrails
+    uses: wealthsimple/github-workflows/.github/workflows/guardrails.yml@v1
+    secrets: inherit