Use simdutf8 for SIMD accelerated utf8 validation?

Hi @BurntSushi ,
Was thinking of submitting a PR to use the simdutf8 crate for SIMD accelerated utf8 validation.

https://github.com/rusticstuff/simdutf8

The benchmarks look pretty good:
https://crates.io/crates/simdutf8

And its used by a lot of high-profile crates:
https://crates.io/crates/simdutf8/reverse_dependencies

I successfully used it in a rust-csv fork I was using earlier, but I was hoping to just keep using the release version of the csv crate.

Is this something that you would consider merging?

The issue names no repository files, tests, or entry points. Start by reviewing the simdutf8 crate and its documented benchmarks, then locate the CSV crate's UTF-8 validation path and assess whether integration is appropriate. Done would require an agreed scope and a benchmark-supported implementation decision.

Written by the indexing model from the issue text.