Document the embed etcd configurations and their usage

[rleungx]

We should add a new sub page to our developer guide to document how GRPCAdditionalServerOptions can be used for changing the default internal gRPC configuration.

	// GRPCAdditionalServerOptions is the additional server option hook
	// for changing the default internal gRPC configuration. Note these
	// additional configurations take precedence over the existing individual
	// configurations if present. Please refer to
	// https://github.com/etcd-io/etcd/pull/14066#issuecomment-1248682996
	GRPCAdditionalServerOptions []grpc.ServerOption `json:"grpc-additional-server-options"`

See etcd-io/etcd#14066 (comment)

[samuelbartels20]

@jmhbnz Please assign me, and I will get it done.