Guide to introduce users to the experimental APIs

Discussed in: https://github.com/kubernetes-sigs/gateway-api-inference-extension/pull/1644/files#r2383572736

We should have a guide that shows a user how to install our experiemental APIs with a _brief_ guide on how to use them, and links to further reading. Given that the APIs are experimental, there will be more expected instability, and so the guides need not be as intensive 