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

system/utilities/miscellaneous.nix

@@ -10,5 +10,7 @@
     rsync
     cryptsetup
     home-manager
+    tree
+    btop
   ];
 }