www/angie-module-zstd: New port: zstd compression for angie

The module adds support for Zstandard compression of responses, both
dynamic (on-the-fly) and static (precompressed files). Compared to gzip,
zstd offers higher compression and decompression speeds at comparable
or better compression ratios.

Source and documentation:
https://github.com/tokers/zstd-nginx-module/

Angie-specific documentation:
https://en.angie.software/angie/docs/installation/external-modules/zstd/

PR: 291546