Expose the method of clearing the cache

I'm using the plugin, but at some point I need to clear the webview cache, so I'd like, if possible, expose the method of clearing the cache, so I can use it wherever I am and however I want, without having to go through launch().

But if there is another way to clear the cache without using launch, please let me know how.
Thanks for listening and for the support.

该请求涉及插件的 launch() 路径及其现有的 webview 缓存清理行为；首先定位该入口点以及 Flutter 端和原生端的缓存操作。定义公共 API 边界，并确认无需调用 launch() 也可以执行清理；然后检查仓库中现有的测试或可手动验证的行为。

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