improve attribution for code ported from zlib-ng

[nmoinvaz]

Hey, first I want to say the README attribution is appreciated — it's good that zlib-ng is acknowledged.

One thing I'd love to see going forward: when specific algorithms or optimizations are ported from zlib-ng, a note in the commit message pointing back to the original commit and author. You can use a Co-authored-by message trailer, a reference like zlib-ng/zlib-ng@commitsha, or simply a message saying "ported from zlib-ng". As an alternative, adding credits to the top of the ported file would also work.

The README mention is a good start, but it's the bare minimum. A lot of the work in zlib-ng represents significant effort by individual contributors, and it's demoralizing to see it quietly reappear elsewhere with no clear path back to the people who did it.

It's also worth knowing that getting some of that code into zlib-ng required personally reaching out to original authors to get them to agree to relicense their work. When that code is ported without attribution, the trail back to those people is lost — and they deserve to be recognized for both their work and the good faith they showed.

[folkertdev]

I've been meaning to get to this, especially for some of the SIMD and compression work that does seem fair.