feature: Add lazyvim.plugins.extras.lang.nix

[izelnakri]

Did you check the docs?

• I have read all the LazyVim docs

Is your feature request related to a problem? Please describe.

Nix is getting more and more popular and becoming almost a standard. I've realized after migrating to LazyVim this week that LazyVim doesnt have a direct support for nix. Currently I'm investigating how to implement all the necessary DX enhancements manually, would be great to have it configured with a single line import just like my other language configurations in LazyVim.

Describe the solution you'd like

Described above.

Describe alternatives you've considered

Currently making a manual solution, will take me most likely 1-2 weeks.

Additional context

I'll implement this regardless and might create a PR with my solution. However still creating this issue in case if someone already has a configuration or wants to make a PR before me. Thanks!

[izelnakri]

Added the initial version of nix language support here: #2956