Replace the webviewx package with webview_flutter_web. (#761)

lib/src/web/web_unity_widget_view.dart

@@ -1,5 +1,5 @@
 import 'package:flutter/material.dart';
-import 'package:webviewx/webviewx.dart';
+import 'package:webview_flutter/webview_flutter.dart';
 
 class WebUnityWidgetView extends StatefulWidget {
   const WebUnityWidgetView({
@@ -16,6 +16,11 @@ class WebUnityWidgetView extends StatefulWidget {
 }
 
 class _WebUnityWidgetViewState extends State<WebUnityWidgetView> {
+  final WebViewController _controller = WebViewController()
+    ..loadRequest(
+      Uri.parse('${Uri.base.origin}/UnityLibrary/index.html'),
+    );
+
   @override
   void initState() {
     super.initState();
@@ -29,13 +34,6 @@ class _WebUnityWidgetViewState extends State<WebUnityWidgetView> {
 
   @override
   Widget build(BuildContext context) {
-    return WebViewX(
-      initialContent: '${Uri.base.origin}/UnityLibrary/index.html',
-      initialSourceType: SourceType.url,
-      javascriptMode: JavascriptMode.unrestricted,
-      onWebViewCreated: (_) {},
-      height: MediaQuery.of(context).size.height,
-      width: MediaQuery.of(context).size.width,
-    );
+    return WebViewWidget(controller: _controller);
   }
 }

pubspec.yaml

@@ -19,7 +19,8 @@ dependencies:
   flutter_plugin_android_lifecycle: ^2.0.7
   stream_transform: ^2.0.0
   plugin_platform_interface: ^2.1.2
-  webviewx: ^0.2.1
+  webview_flutter: ^4.0.0
+  webview_flutter_web: ^0.2.2
 #  ffi: ^1.2.1 // required for windows support
 
 dev_dependencies: