docs: add NVIDIA Dynamo integration guide

[danehans]

Once ai-dynamo/dynamo#7607 merges, agentgateway will be supported as an NVIDIA Dynamo inference gateway. The integration should be highlighted in the integration guides and/or in the current k8s inference routing docs.

[npolshakova]

Let's move the docs issues to https://github.com/agentgateway/website