Support for msgpack encoder

[rohsaini]

My Usecase:
I use zerolog logging library along with fluentbit. fluentbit input plugin used is forward (https://docs.fluentbit.io/manual/pipeline/inputs/forward).
zerolog encodes the log and sends it fluentbit over tcp channel.

Problem:
Currently, zerolog supports json or CBOR as encoder at compile time. fluentbit forward plugin supports only msgpack binary encoding/decoding. So, there is need for support for msgpack encoding implicitly by zerolog.