add msgpack library

[cthulhu-irl]

Description

Parsi is a parser combinator library and it has core building blocks to make parsers, but it also would be much nicer to provide serializer/deserializer for common simple data formats.

MsgPack as binary data format alternative to json is simple, powerful, and also easy to parse compared to json. It is also a good candidate to benchmark.

Goals

• bring parsi to real world use cases.
• provide builtin parser for the very common yet simple data formats.

Definition of Done

• there must be a mini library that can serialize and deserialize standard message pack format.
• parsers must be visit-based and preferably allocation-free.
• nested parsers must not rely on call stack and recursion.