refactor: remove global window assignment for Artplayer and template export

- Removed the assignment of Artplayer to the global window object in index.js of the artplayer package.
- Eliminated the window export for the template plugin in index.js, streamlining the code and reducing global scope pollution.

packages/artplayer/src/index.js

@@ -255,8 +255,6 @@ Artplayer.USE_RAF = false
 Artplayer.REMOVE_SRC_WHEN_DESTROY = true
 
 if (utils.isBrowser) {
-  window.Artplayer = Artplayer
-
   utils.setStyleText('artplayer-style', style)
 
   setTimeout(() => {