title: Flutter InAppWebView does not allow non english content in textfield
body: <p>I'm having a weird issue with the Flutter InAppWebView plugin version 4.0.0+4 here <a href="https://pub.dev/packages/flutter_inappwebview" rel="nofollow noreferrer">https://pub.dev/packages/flutter_inappwebview</a> where I try to load the simple contact us form into the plugin and realize that I can't enter the content into html input text field if I use non English keyboard, in my case I use Vietnamese keyboard. If I switch the keyboard to English one then its working. I double checked the contact us form and made sure its working 100% on Chrome browser outside of the Flutter app using even non English keyboard. I don't use any special code or settings for the plugin, just same as the one mentioned in the pub.dev. I'm using Flutter channel stable v. 1.22.6</p>
  <p>This is my code in case you need it:</p>
  <pre><code>
  class WebViewerWidget extends StatefulWidget {
    final Map&lt;String, String&gt; metaData;
  
    WebViewerWidget({this.metaData});
  
    @override
    _WebViewerWidgetState createState() =&gt; _WebViewerWidgetState();
  }
  
  class _WebViewerWidgetState extends State&lt;WebViewerWidget&gt; {
    @override
    void initState() {
      super.initState();
    }
  
    @override
    Widget build(BuildContext context) {
      InAppWebViewController _webviewCtrl;
      double progressIndicator = 0;
      return Scaffold(
          backgroundColor: ColorPalette.white,
          appBar: PreferredSize(
            child: TopNavWidget(
              title: widget.metaData['title'] ?? '',
            ),
            preferredSize: Size.fromHeight(50.0),
          ),
          body: Builder(
            builder: (BuildContext context) {
              return Container(
                child: Column(
                  children: [
                    Container(
                        child: progressIndicator &lt; 1
                            ? LinearProgressIndicator(
                                value: progressIndicator,
                                backgroundColor: Colors.black12,
                                valueColor:
                                    AlwaysStoppedAnimation&lt;Color&gt;(Colors.blue),
                              )
                            : Container()),
                    Expanded(
                      child: InAppWebView(
                        initialUrl: widget.metaData['url'] ?? 'about:blank',
                        initialOptions: InAppWebViewGroupOptions(
                          crossPlatform: InAppWebViewOptions(
                            debuggingEnabled: true,
                            javaScriptEnabled: true,
                            useShouldInterceptAjaxRequest: true,
                            useShouldInterceptFetchRequest: true,
                          ),
                          ios: IOSInAppWebViewOptions(),
                          android: AndroidInAppWebViewOptions(),
                        ),
                        onWebViewCreated:
                            (InAppWebViewController webviewController) {
                          _webviewCtrl = webviewController;
                        },
                        onProgressChanged:
                            (InAppWebViewController controller, int progress) {
                          setState(() {
                            progressIndicator = progress / 100;
                          });
                        },
                      ),
                    ),
                  ],
                ),
              );
            },
          ));
    }
  }
  
  </code></pre>
  <p>Thanks.</p>