feat(darwin)!: update config

Add `nix` initialization script to shell's `extraConfig`
  - fixes `nix` when updating MacOS
Add `flameshot` to `brew` packages
Fix tilde (`~`) remapping
  - mysteriously switched after a restart, needed to swap
Add (noncompiling) `borders` (`JankyBorders`) config
Add `TODO` to `sketchybar` config

modules/nix-darwin/yabai/sketchybar/default.nix

@@ -1,4 +1,5 @@
 # TODO: AppleSelectedInputSourcesChangedNotification
+# TODO: no `PLUGIN_DIR` and `UTIL_DIR`, directly reference scripts
 { lib, darwin, ... }:
 
 let