chore: Add import check

I have no idea what this does.

flake.nix

@@ -18,6 +18,8 @@
           propagatedBuildInputs =
             [ click marshmallow mistune pygments pyyaml urwid ];
 
+          pythonImportsCheck = [ "lookatme" ];
+
           nativeBuildInputs = [ setuptools ];
         };
     }) nixpkgs.legacyPackages;