save/restore custom app groups

examples/app_library/utils.rs

@@ -0,0 +1,11 @@
+use std::path::PathBuf;
+
+use gtk4::glib;
+
+pub fn data_path() -> PathBuf {
+    let mut path = glib::user_data_dir();
+    path.push("com.cosmic.app_library");
+    std::fs::create_dir_all(&path).expect("Could not create directory.");
+    path.push("data.json");
+    path
+}