Add Nix Shell support

Author: fedx-sudo

Diff for: shell.nix

@@ -0,0 +1,9 @@
+{ pkgs ? import <nixpkgs> {} }:
+let
+  myAppEnv = pkgs.poetry2nix.mkPoetryEnv {
+    projectDir = ./.;
+    editablePackageSources = {
+      my-app = ./src;
+    };
+  };
+in myAppEnv.env