Add support for BLAKE3 hashing

[cameronfyfe]

Description

I'm working on some data provenance tooling that tracks files and blobs primarily using BLAKE3 hashes. I would like to make some instances of my data schema interoperable with the Manifest class in this package without having to re-hash any data during the conversion.

If "blake3" is added as a supported payload hashing algorithm, I should be able to support interoperability with this model.

I can probably submit a PR when time allows if there's no problem with adding this.