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/assets/ts/artplayer-tool-iframe.d.ts

@@ -4,7 +4,7 @@ interface Message {
   id?: number
 }
 
-declare class ArtplayerPluginIframe {
+declare class ArtplayerToolIframe {
   constructor(option: { iframe: HTMLIFrameElement, url: string })
 
   static iframe: boolean
@@ -26,7 +26,7 @@ declare class ArtplayerPluginIframe {
   destroy(): void
 }
 
-export default ArtplayerPluginIframe
+export default ArtplayerToolIframe
 
-export = artplayerPluginIframe
-export as namespace artplayerPluginIframe;
+export = artplayerToolIframe
+export as namespace artplayerToolIframe;