Add support for zstd as a compression algorithm

[extesy]

Zstandard (also known as zstd) has a great speed and compression ratio tradeoff. It also has a backing of a huge company (Facebook) and its repo is very active. I would love to be able to use zstd with configurable compression strength in SharpCompress. On its highest setting it is comparable to PPMd for compression ratio, but faster.

[adamhathcock]

It would be cool but this is something I'm personally unwilling to do. In fact I didn't port any algorithm since the original RAR.

Looking at their page there is a full java decoder that could be ported to C#. I wouldn't want just a wrapper of the native DLL in sharpcompress as that's not all platforms.

[samuel-w]

I found a partial implementation of it, compression only. https://github.com/mcraiha/CSharp-zstd

[adamhathcock]

Thanks. Keeping this open

[samuel-w]

I found another one, seems to have both compress and decompress https://github.com/oleg-st/ZstdSharp

[adamhathcock]

Got an itch and started

Compression from: https://github.com/oleg-st/ZstdSharp
File format from the RFC: https://datatracker.ietf.org/doc/html/rfc8878#section-3.1
WIP here: #627