feat: introduce ArtplayerToolIframe for iframe control

- Removed the old ArtplayerPluginIframe implementation.
- Added ArtplayerToolIframe class with methods for iframe communication.
- Implemented postMessage and onMessage methods for message handling.
- Created a new TypeScript definition file for ArtplayerToolIframe.
- Updated documentation links to point to the new iframe tool.
- Added npm ignore file and README for the new package.
- Included compiled and uncompiled versions of the new iframe tool.
- Updated package.json with relevant metadata and exports.

docs/test/index.html

@@ -38,7 +38,7 @@
     <script src="../compiled/artplayer-plugin-danmuku.js"></script>
     <script src="../compiled/artplayer-plugin-dash-control.js"></script>
     <script src="../compiled/artplayer-plugin-hls-control.js"></script>
-    <script src="../compiled/artplayer-plugin-iframe.js"></script>
+    <script src="../compiled/artplayer-tool-iframe.js"></script>
     <script src="../compiled/artplayer-plugin-vtt-thumbnail.js"></script>
     <script src="../compiled/artplayer-plugin-chapter.js"></script>
     <script src="https://cdnjs.cloudflare.com/ajax/libs/hls.js/1.5.17/hls.min.js"></script>