feat: introduce development shell configuration

.envrc

@@ -0,0 +1,2 @@
+use flake
+

flake.nix

@@ -71,6 +71,9 @@
     packages = forAllSystems ({pkgs}: import ./pkgs {inherit pkgs;});
     overlays = import ./overlays {inherit inputs lib;};
     formatter = forAllSystems ({pkgs}: pkgs.alejandra);
+    devShells = forAllSystems ({pkgs}: {
+      default = import ./shell.nix {inherit pkgs;};
+    });
 
     nixosConfigurations = listToAttrs (map (hostname: {
         name = hostname;

shell.nix

@@ -0,0 +1,28 @@
+{
+  pkgs ?
+  # If 'pkgs' isn't defined, instantiate 'nixpkgs' from locked commit.
+  let
+    lock = (builtins.fromJSON (builtins.readFile ./flake.lock)).nodes.nixpkgs.locked;
+    nixpkgs = fetchTarball {
+      url = "https://github.com/NixOS/nixpkgs/archive/${lock.rev}.tar.gz";
+      sha256 = lock.narHash;
+    };
+  in
+    import nixpkgs {},
+}:
+pkgs.mkShell {
+  NIX_CONFIG = "extra-experimental-features = nix-command flakes";
+
+  packages = with pkgs; [
+    nix
+    git
+    neovim
+    fzf
+
+    # Code Linting.
+    statix
+    deadnix
+    alejandra
+    flake-checker
+  ];
+}