Expose `Buffer#utf8Slice`

I'm using this package (version 6.0.3) to run [undici](https://github.com/nodejs/undici) in browser.

Undici contains a call to `Buffer#utf8Slice`:

https://github.com/nodejs/undici/blob/cab60114da8bf9acc6628daff2ab58f06856bbc9/lib/api/readable.js#L328

Admittedly it's not in the documentation, but as it's in Undici and not Node.js core repository, I guess it could be considered part of the public interface?

Can this package be updated to expose that? (I'm monkey patching this library to do that so it's not an urgency)