feature(shell): add zsh home-manager module

modules/home-manager/shell.nix

@@ -0,0 +1,20 @@
+{ config, pkgs, inputs, ... }:
+ 
+{
+  programs.zsh = {
+    enable = true;
+    autosuggestion.enable = true;
+    syntaxHighlighting.enable = true;
+    oh-my-zsh = {
+      enable = true;
+      theme = "agnoster";
+      #plugins = [ "git" "ssh-agent" ];
+    };
+  };
+
+  # set important env vars
+  home.sessionVariables = {
+    EDITOR = "vim";
+    NH_FLAKE = "/home/aaron/git/nixconfig";
+  };
+}