Improve the GHA workflow for triggering a new Cloudflare Pages Deployments

This is a follow-up for #42 and #44.

Further improvements we could make in the future:

1. Add `| tee response.json`, use `jq` to extract `result.id` and print URL where to watch deployment status:
   ```
   https://dash.cloudflare.com/${CLOUDFLARE_ACCOUNT_ID}/pages/view/${PROJECT_NAME}/${body.result.id}
   ```

2. Remove the step "Install Node.js", we don't need Node anymore.