Add support for Nix-PKGS

[CelestifyX]

Pls, add support for NIXOS Package Manager (Count packages) :)

[CelestifyX]

@LivacoNew

use std::env;
use std::process::Command;

fn process_nix_system_packages() -> Option<u64> {
    let output = Command::new("nix-store").args(&["-q", "--requisites", "/run/current-system/sw"]).output().ok()?;
    Some(output.stdout.lines().count() as u64)
}

fn process_nix_user_packages() -> Option<u64> {
    let home_dir = env::var("HOME").ok()?;
    let output   = Command::new("nix-store").args(&["-q", "--requisites", &format!("{}/.nix-profile", home_dir)]).output().ok()?;

    Some(output.stdout.lines().count() as u64)
}

[LivacoNew]

Not gonna go down the path of using commands before eliminating caches or package databases like other managers, installing a VM as we speak to play around with it.

[CelestifyX]

Yes, but there is no other way