Making HSLuv in line with modern GitHub workflows

[boronine]

Until recently HSLuv used Nix, some techniques were even described on my blog. Brilliant as Nix is, on balance it became a liability, making it harder for people to contribute. I have also struggled with Haxe packaging in Nix, and was sad to discover that Haxe is broken on arm64 Nix (edit: macOS). I had to come up with workarounds for these issues. All in all, Nix had to go.

Much of the feeling of security provided by Nix can be had with a procedural CI system, and embracing GitHub Actions seemed like the obvious choice. So I made a big move:

• Haxe moved to its own repo: https://github.com/hsluv/hsluv-haxe (w/ automated testing)
• New Haxe version released with a new API that avoids heap allocation (about 2x speed improvement): https://lib.haxe.org/p/hsluv/
• JavaScript implementation moved to its own repo: https://github.com/hsluv/hsluv-javascript
• JS implementation transpiled from Haxe, then manually converted to TypeScript
• New JS implementation is a pre-release on npm (breaking change): https://www.npmjs.com/package/hsluv/v/1.0.0-rc2
• JS implementation has automated build, testing and npm publishing
• Main repo is now dedicated to hsluv.org website, math and shared secrets: https://github.com/hsluv/hsluv
• The build system for hsluv.org website is a plain Node.js environment: https://github.com/hsluv/hsluv/blob/master/package.json
• The main repo has automation for publishing the master branch
• Static website is now hosted on GitHub Pages: https://github.com/hsluv/hsluv/tree/gh-pages

Thanks to @hartwork for bringing some of these issues to my attention and inspiring this move.