docs: link the live playground

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: DanMat

README.md

@@ -83,7 +83,7 @@ Constructor options extend the key options above plus `maxEntries`, `ttl` (ms),
 - **`@danmat/query-cache`** — body-aware response caching *(you are here)*.
 - [`@danmat/query-server`](https://github.com/DanMat/query-server) — server-side request validation & negotiation.
 
-▶️ **See them work together:** [query-suite-example](https://github.com/DanMat/query-suite-example) — a runnable stock-screener demo using all four.
+▶️ **See them work together:** [query-suite-example](https://github.com/DanMat/query-suite-example) — a runnable demo using all four, with a **[🌐 live playground](https://query-suite-example.danmat.workers.dev)**.
 
 ## License