Switch back to Vim

- Change default editor back to vim since doom-emacs is broken at the
  moment
- Conditionally include emacs or vim nix files in configuration.nix
- User username to find dwm-flexipatch path on system
- Add tree and btop to miscellaneous system packages
- Add some cli tools like just and git to home-manager packages
- Add more XDG env vars for config and cache

flake.nix

@@ -39,7 +39,7 @@
         theme = "dracula";            # Selected theme from themes directory
         browser = "vivaldi";          # Default browser
         term = "kitty";               # Default terminal command
-        editor = "emacsclient";       # Default editor
+        editor = "vim";               # Default editor
         spawnEditor =
           if (editor == "emacsclient") then
             "emacsclient -c -a 'emacs'"