title: clearCache of flutter_webview_plugin package doesn't work
body: <p>I use the WebView_plugin in my Flutter project. I can load my own website. But my website updates aren't there. I guess it's a cache issue.</p>
  
  <p>I tried to pass some options like: <code>clearCache</code>, <code>appCacheEnabled</code> but my website updates aren't there.</p>
  
  <p>How I instantiate my webview: </p>
  
  <pre><code>dart 
      final webView = WebviewScaffold(
        url: url,
        clearCache: true, // &lt;-- I don't want cache 
        appCacheEnabled: false, // &lt;-- I don't want cache
        initialChild: Container(
          color: Colors.white,
          child: const Center(
            child: const CircularProgressIndicator(),
          ),
        ),
        withZoom: false,
        withLocalStorage: true,
        hidden: true,
      );
  </code></pre>
  
  <p>In my <code>pubspec.yaml</code>:</p>
  
  <pre><code>dependencies:
    flutter_webview_plugin: ^0.3.5
  </code></pre>
  
  <p>How do I clear the cache?</p>