[new feature] Docs & examples of using envoy mesh for routing

[foxish]

New feature or functionality
What would you like Signadot to do?

For users that directly use envoy as a mesh rather than a full fledged mesh control plane like istio, this item covers documentation to configure the envoy mesh with filters to enable sandbox routing. It would also represent the graduation of the configuration in https://github.com/signadot/examples/tree/main/experimental/custom-routing-with-envoy.

Additional considerations
Anything in particular to think about regarding this new feature?