Documentation / examples for DynamoDB HTTP Filter

*Description*:

We're interested in trying out the HTTP DynamoDB filter, but the documentation is a bit light on. I'd love to see a more end-to-end example of what's involved in using it.

For example, are the teams at Lyft overriding the endpoint to `localhost:` and setting a `Host` header? Is there an Envoy sidecar capturing _all_ outgoing traffic from a process/container using a network policy? Is there special handling for TLS?

Also, if anyone can help point me in the right direction, I'm happy to open a PR updating the documentation with a more concrete example.

Thanks!

*Relevant Links*

Architecture Docs: https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/dynamo
Current configuration examples:
https://github.com/envoyproxy/envoy/blob/ed9e04277328486d397ce074517516824a877922/configs/envoy_service_to_service_v2.template.yaml#L262-L266
https://github.com/envoyproxy/envoy/blob/ed9e04277328486d397ce074517516824a877922/configs/configgen.py#L44-L66
Mention of external service egress listeners: https://www.envoyproxy.io/docs/envoy/latest/intro/deployment_types/service_to_service#optional-external-service-egress-listeners