overlays/nixpkgs-unstable: init

Using for some darwin specific packages until I figure out a proper
module pkg inheritance in snowfall or just switch to flake-parts or
something else.

overlays/nixpkgs-unstable/default.nix

@@ -0,0 +1,22 @@
+{ channels, ... }:
+_final: _prev: {
+  inherit (channels.nixpkgs-unstable)
+    # Core
+    jankyborders
+    raycast
+    sketchybar
+    skhd
+    yabai
+
+    # Misc
+    alt-tab-macos
+    appcleaner
+    bartender
+    blueutil
+    duti
+    mas
+    monitorcontrol
+    stats
+    switchaudio-osx
+    ;
+}