add wiki page for nix

Author: o2sh

docs/wiki/Home.md

@@ -4,9 +4,10 @@ Welcome to the onefetch's wiki!
 - **General**
   - [Installation](https://github.com/o2sh/onefetch/wiki/installation)
   - [Getting started](https://github.com/o2sh/onefetch/wiki/getting-started)
+  - [Nix local setup](https://github.com/o2sh/onefetch/wiki/nix-local-setup)
 - **Options**
   - [Command-line options](https://github.com/o2sh/onefetch/wiki/command-line-options)
 - **Images**
-  - [Images in the terminal](https://github.com/o2sh/onefetch/wiki/Images-in-the-terminal)
+  - [Images in the terminal](https://github.com/o2sh/onefetch/wiki/images-in-the-terminal)
 - **Ascii**
   - [Ascii art](https://github.com/o2sh/onefetch/wiki/ascii-art)

docs/wiki/_Sidebar.md

@@ -2,6 +2,7 @@
 - **General**
   - [Installation](https://github.com/o2sh/onefetch/wiki/installation)
   - [Getting started](https://github.com/o2sh/onefetch/wiki/getting-started)
+  - [Nix local setup](https://github.com/o2sh/onefetch/wiki/nix-local-setup)
 - **Options**
   - [Command-line options](https://github.com/o2sh/onefetch/wiki/command-line-options)
 - **Images**

docs/wiki/nix-local-setup.md

@@ -0,0 +1,54 @@
+# Nix as a Development Environment
+
+[Nix](https://nixos.org/) is a package manager that uses a purely functional approach to dependency management. Packages in Nix are built and run in isolated, reproducible environments. This tutorial walks you through setting up a development environment for [Onefetch](https://github.com/o2sh/onefetch) using Nix.
+
+> This guide assumes you already have Nix [installed](https://nixos.org/download.html#nix-quick-install) on your system.
+
+## Setup
+
+To begin, create a `flake.nix` file with the following content:
+
+```nix
+{
+  description = "onefetch";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    ...
+  }: let
+  forAllSystems = fn: nixpkgs.lib.genAttrs [
+    "aarch64-darwin"
+    "aarch64-linux"
+    "i686-linux"
+    "x86_64-linux"
+    "x86_64-darwin"
+  ] (system: fn nixpkgs.legacyPackages.${system});
+  in {
+    devShells = forAllSystems (pkgs: {
+      default = pkgs.mkShell {
+        name = "onefetch";
+        packages = with pkgs; [
+          cargo
+          rustc
+          clippy
+          rustfmt
+          rust-analyzer
+          cmake
+        ];
+        RUST_SRC_PATH = "${pkgs.rust.packages.stable.rustPlatform.rustLibSrc}";
+      };
+    });
+  };
+}
+```
+
+then enter the development shell:
+
+```bash
+nix develop
+```