This introduces a new type ProtoJSONStream. This type wraps an io.ReadCloser that represents a JSON stream formatted as a JSON array, and decodes each item (which are JSON Objects) into a predefined Protobuf message type. The primary use case is to enable clients to decode HTTP-JSON server-streams into protobuf messages as needed.

This could later be extended to support writing to a stream (e.g. the Write end of an open pipe used as a HTTP Request body) in the same format.