add nix and direnv configuration

.envrc

@@ -0,0 +1,13 @@
+mkdir -p .nix-mix
+mkdir -p .nix-hex
+
+export LANG=en_US.UTF-8
+export ERL_AFLAGS="-kernel shell_history enabled"
+
+use nix
+
+export MIX_HOME=$PWD/.nix-mix
+export HEX_HOME=$PWD/.nix-hex
+
+PATH_add $MIX_HOME/bin
+PATH_add $HEX_HOME/bin

shell.nix

@@ -0,0 +1,45 @@
+{
+  lib ? import <lib> {},
+  pkgs ? import (fetchTarball https://github.com/NixOS/nixpkgs/tarball/nixos-24.05){
+    config.allowUnfree = true;
+  }
+}:
+
+let
+
+
+  # define packages to install with special handling for OSX
+  basePackages = [
+    pkgs.gnumake
+    pkgs.gcc
+    pkgs.readline
+    pkgs.zlib
+    pkgs.libxml2
+    pkgs.libiconv
+    pkgs.openssl
+    pkgs.git
+    pkgs.python3
+
+    pkgs.postgresql
+
+    pkgs.elixir_1_16
+    pkgs.nodejs_18
+    pkgs.yarn
+    pkgs.license_finder
+
+    pkgs.gh
+    pkgs.ripgrep
+    pkgs.jq
+  ];
+
+  inputs = basePackages
+    ++ [ pkgs.bashInteractive ]
+    ++ pkgs.lib.optionals pkgs.stdenv.isLinux [ pkgs.inotify-tools ]
+    ++ pkgs.lib.optionals pkgs.stdenv.isDarwin (with pkgs.darwin.apple_sdk.frameworks; [
+        CoreFoundation
+        CoreServices
+      ]);
+
+in pkgs.mkShell {
+  buildInputs = inputs;
+}