feat(nix-darwin): add setbg script

Sets the background of all spaces on all displays/desktops to an image (passed as a command-line argument) preserving the focused spaces and window after running
Depends on `yabai` (>`System Integrity Protection must be partially disabled.`) and `jq`
Written in `applescript`

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

@@ -0,0 +1,27 @@
+{ lib
+, writeShellScriptBin
+, symlinkJoin
+, makeWrapper
+, jq
+, yabai
+}:
+
+let
+  # NOTE: passing `${1}` because `${0}` resolves to the `.setbg-wrapped` path
+  setWallpaperUnwrapped =
+    writeShellScriptBin "setbg" ''
+      osascript ${./setbg.scpt} "''${1}"
+    '';
+in
+  symlinkJoin {
+    name = "setbg";
+    paths = [ setWallpaperUnwrapped ];
+    buildInputs = [ makeWrapper ];
+    postBuild = ''
+      wrapProgram $out/bin/setbg \
+        --prefix PATH : ${lib.makeBinPath [
+          jq
+          yabai
+        ]}
+    '';
+  }