msgpack: Improve perf

[cometkim]

Following the #1, #6

The final condition for this package to be adopted is probably the performance.

It already has an advantage in terms of bundle size and compatibility, but we don't want to leave performance as an area of trade-off

[cometkim]

I'm going to try Rewriting in ReScript for the Encoder as well, as I've seen the improvements from #6.

I can provide settings for ReScript if anyone wants.