feat(lang): nix add statix linter (#6244)

## Description

Adds [`statix`](https://github.com/oppiliappan/statix) linter to
`lang/nix.lua` using `nvim-lint`

## Related Issue(s)

None

## Screenshots


## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

lua/lazyvim/plugins/extras/lang/nix.lua

@@ -24,4 +24,13 @@ return {
       },
     },
   },
+  {
+    "mfussenegger/nvim-lint",
+    optional = true,
+    opts = {
+      linters_by_ft = {
+        nix = { "statix" },
+      },
+    },
+  },
 }