Add Nix package instructions to README

[Br1ght0ne]

I added a Nix package for gex in https://github.com/NixOS/nixpkgs/pull/196931.

[Piturnah]

Thanks for this PR! I'm not familiar at all with Nix so my main question here is will I need to maintain keeping the nix package up to date with new releases?

[Piturnah]

From the nixpkgs README:

The Nixpkgs maintainers are people who have assigned themselves to maintain specific individual packages. We encourage people who care about a package to assign themselves as a maintainer. When a pull request is made against a package, OfBorg will notify the appropriate maintainer(s). The Nixpkgs committers are people who have been given permission to merge.

So the way I understand it is that you are signing yourself up to maintain the gex package on nixpkgs?

[Br1ght0ne]

@Piturnah

will I need to maintain keeping the nix package up to date with new releases?

I will do that myself. I use software to maintain all packages I add to Nixpkgs myself. Don't worry :)

So the way I understand it is that you are signing yourself up to maintain the gex package on nixpkgs?

Yes. I maintain quite a few, and that usually amounts to (seeing new release notification - updating a few hashes - making a PR to nixpkgs). I do this to help out the communities, especially with Rust projects :)

EDIT: there's also https://github.com/r-ryantm bot which does automatic updates for compatible packages (Rust crates included), so often there's next to no manual overhead.

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Also I can add a badge like this to your README (if you prefer, of course), using [Repology] to list all repositories the package appears in. Nix packages are included, crates.io is not on the list, but you use a badge already. This uses sozu package as an example:

[Piturnah]

Thank you for clarifying, and thanks for your contribution!