chore: add nix script

shell.nix

@@ -0,0 +1,27 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+let
+  erlang = pkgs.beam.interpreters.erlang_25;
+  elixir = pkgs.beam.packages.erlang_25.elixir;
+  gleam = pkgs.gleam;
+in
+pkgs.mkShell {
+  buildInputs = [
+    erlang
+    elixir
+    gleam
+  ];
+
+  shellHook = ''
+    echo "Erlang, Elixir, and Gleam development environment"
+    echo "================================================"
+    echo "Erlang version: $(erl -eval 'erlang:display(erlang:system_info(otp_release)), halt().' -noshell)"
+    echo "Elixir version: $(elixir --version)"
+    echo "Gleam version: $(gleam --version)"
+    echo ""
+    echo "To start Erlang shell, type: erl"
+    echo "To start Elixir shell, type: iex"
+    echo "To start a new Gleam project, type: gleam new project_name"
+    echo "================================================"
+  '';
+}