feat(window-state): support using a custom filename (#1138)

* feat(window-state): support using a custom filename

ref: https://github.com/tauri-apps/plugins-workspace/pull/1079

* generate api

* fmt

plugins/window-state/src/cmd.rs

@@ -32,3 +32,8 @@ pub async fn restore_state<R: Runtime>(
         .map_err(|e| e.to_string())?;
     Ok(())
 }
+
+#[command]
+pub fn filename<R: Runtime>(app: AppHandle<R>) -> String {
+    app.filename()
+}