Add chrs installation instructions using nix flakes

docs/chrs/install.md

@@ -55,3 +55,58 @@ If necessary, add the `bin` folder to `$PATH`:
 echo 'export PATH="$HOME/.cargo/bin:$PATH"' >> ~/.bashrc
 source ~/.bashrc
 ```
+
+## Home Manager using Nix Flakes
+
+Edit `~/.config/home-manager/flake.nix`
+
+```nix
+{
+  description = "Home Manager configuration example";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+    home-manager = {
+      url = "github:nix-community/home-manager";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    chrs.url = "github:FNNDSC/chrs";  # <-- add this line
+  };
+
+  outputs = { nixpkgs, home-manager, ... } @ inputs:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+    in {
+      homeConfigurations."chris@computer" = home-manager.lib.homeManagerConfiguration {
+        inherit pkgs;
+        modules = [
+          ./packages.nix  # <-- file where chrs will be specified
+        ];
+        extraSpecialArgs = { inherit inputs; };  # <-- pass inputs to modules
+      };
+    };
+}
+```
+
+And create the file `~/.config/home-manager/packages.nix` with the content:
+
+```nix
+{ lib, pkgs, inputs, ... }:
+
+{
+  home.packages = with pkgs; [
+    inputs.chrs.packages.${system}.default
+  ];
+}
+```
+
+Run
+
+```shell
+cd ~/.config/home-manager
+git add flake.nix packages.nix
+nix flake update
+git add flake.lock
+home-manager switch
+```