modules updates

modules/shell/exercism.nix

@@ -0,0 +1,11 @@
+{ config, lib, pkgs, unstable, ... }:
+
+{
+  options.my.shell.exercism.enable = lib.mkEnableOption "enable";
+  config = lib.mkIf config.my.shell.exercism.enable {
+    users.users.jawz.packages = with pkgs; ([
+      exercism # learn to code
+      bats # testing system, required by Exercism
+    ]);
+  };
+}