feat: add Renovate CLI as DevContainer feature

- Add ghcr.io/devcontainers-extra/features/renovate-cli:2 to devcontainer.json
- Ensures Renovate CLI is available in every environment startup
- Removes need for manual npm install -g renovate

Author: loujaybee

.devcontainer/devcontainer.json

@@ -18,7 +18,8 @@
     "ghcr.io/devcontainers/features/docker-in-docker:2": {
       "version": "latest",
       "moby": true
-    }
+    },
+    "ghcr.io/devcontainers-extra/features/renovate-cli:2": {}
   },
   "forwardPorts": [
     3000,