refactor: auto start apps on login via xdg-autostart (#242)

Signed-off-by: Ryan Yin <xiaoyin_c@qq.com>

home/linux/gui/base/xdg/default.nix

@@ -0,0 +1,35 @@
+# XDG stands for "Cross-Desktop Group", with X used to mean "cross".
+# It's a bunch of specifications from freedesktop.org intended to standardize desktops and
+# other GUI applications on various systems (primarily Unix-like) to be interoperable:
+#   https://www.freedesktop.org/wiki/Specifications/
+{
+  mylib,
+  config,
+  pkgs,
+  ...
+}:
+{
+  imports = mylib.scanPaths ./.;
+
+  home.packages = with pkgs; [
+    xdg-utils # provides cli tools such as `xdg-mime` `xdg-open`
+    xdg-user-dirs
+  ];
+
+  xdg = {
+    enable = true;
+
+    cacheHome = "${config.home.homeDirectory}/.cache";
+    configHome = "${config.home.homeDirectory}/.config";
+    dataHome = "${config.home.homeDirectory}/.local/share";
+    stateHome = "${config.home.homeDirectory}/.local/state";
+
+    userDirs = {
+      enable = true;
+      createDirectories = true;
+      extraConfig = {
+        XDG_SCREENSHOTS_DIR = "${config.xdg.userDirs.pictures}/Screenshots";
+      };
+    };
+  };
+}