Add Zstandard (zstd) Compression Support

[thelovekesh]

This package already features a robust and well-tested archiving API with support for multiple decompression formats. Since it currently depends on github.com/klauspost/compress for zstd decompression, enabling zstd compression as well would be a natural extension.

Zstandard has matured significantly and is increasingly adopted at scale—Chromium, for example, now supports zstd encoding. Enabling compression with zstd would broaden the usability of this package, particularly in high-performance contexts and modern distribution workflows.