ZSTD support

[jschueller]

refreshed #28 without the math changes, and no asm, as requested
also forwarded the new data size argument to zstd

/cc @dbeinder @sredna

[jschueller]

hello @sredna, would it be possible to approve the workflow to at least run the CI ?
ping @dbeinder

[dbeinder]

Thank you for updating my PR! I'm not part of the NSIS team though, so I can't really help you get this merged.

I see you've updated zstd - I had made a few patches to reduce the size of exehead: https://github.com/dbeinder/nsis/blob/d353438eff9244cc2416e1b7bb0b17551a25941d/Source/zstd/zstd-v1.5.6.diff
It basically strips out unused code for unpacking with the help of a separate dictionary file and the built-in XXH64 checksum which should be redundant.

Not sure if this is still worth doing, or if the NSIS team considers minimal exehead size a priority.

[jschueller]

I think its best not to alter the zstd sources for easier maintenance, or changes must be upstreamed first