docs/envoy: include new configurable gRPC msg sizes (#4459)
docs/envoy: include new configurable gRPC msg sizes (#4459)

Docs for https://github.com/open-policy-agent/opa-envoy-plugin/pull/323

Signed-off-by: Elliot Maincourt <17c2c9cc046ccdc466814673659dda164b8cb820@gmail.com>

open-policy-agent/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,tsandall/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,open-policy-agent/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa