WIP feat: add language.nodejs extra

[tennox]

I'm new to nix but managed to throw together
what I needed to have consistent nodejs version for:

node --version
yarn node --version
pnpm node --version

Usage:

imports = ["language/nodejs"]
[language.nodejs]
package = "nodejs-16_x"

I think in the end it might be better or more DRY to use something like:
https://github.com/cprussin/nixjs

But it's a bit outdated and I did not figure out how to define overlays in an extra file. 😢
(I still would love to know)

[tennox]

I figured out now that most of the custom patches are not necessary if you just overlay the default nodejs package:

overlays=[(self: prevPkgs: {nodejs=prevPkgs.nodejs-16_x;})]

So if we can add an overlay in an extra file that would be the the simplest solution 🤔

see also in the discourse

[r17x]

I think it could be like this:

• override nodejs pkg in pkgs.nodePackages

letnodePackages=pkgs.nodePackages.override{nodejs=cfg.package};

• define packages

devshell.packages=[cfg.packagenodePackages.yarnnodePackages.pnpm]

[tennox]

I think I tried this, but don't remember.

I figured that the overlay is much better and will then cover everything dependant on nodejs (e.g. yarn toplevel)

But I don't know how to do that in a devshell extra, do you?