docs: add killercoda demo link (#413)

Signed-off-by: Adam Gardner <adam@agardner.net>
Co-authored-by: Michael Beemer <beeme1mr@users.noreply.github.com>

README.md

@@ -14,6 +14,8 @@
 
 The OpenFeature Operator allows you to expose feature flags to your applications. It injects a [flagD](https://github.com/open-feature/flagd) sidecar into relevant pods exposes gRPC and HTTP interfaces for flag evaluation. To get started, follow the installation instructions in the [docs](./docs).
 
+<h2 align="center"><a href="https://killercoda.com/open-feature/scenario/openfeature-operator-demo" target="_blank">Try the OpenFeature Operator in the Killercoda Playground (in browser)</a></h2>
+
 ## Contributing
 
 See [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute to the OpenFeature project.