fix: update window export syntax for plugin; ensure compatibility with global scope

feat: add example usage for artplayer-plugin-test in test.js

scripts/plugin/template/src/index.js

@@ -27,5 +27,5 @@ if (typeof document !== 'undefined') {
 }
 
 if (typeof window !== 'undefined') {
-    window['{{export}}'] = {{export}};
+    window.{{export}} = {{export}};
 }