[feature request] msgpack and msgpackz loaders

[maxim-uvarov]

Saul, Anja, could you please add support for the msgpack and msgpackz formats? I would love to replace JSON (which works fine anyway) with msgpack for communication between nushell and visidata. I tried to rewrite the current JSON loader for msgpack with the help of GPT, but my attempts failed. So I'm asking you, as it doesn't seem like a very difficult task. 🙏🙏🙏