Fixed iOS userContentController didReceive WKScriptMessage event when…

… using a WebView created with a windowId

added isAvailable ChromeSafariBrowser static method

flutter format

update README.md

v3.4.0

updated example main.dart

release v3.3.0

v3.2.0, added context menu classes, updated docs, fix pichillilorenzo…

…#235, fix pichillilorenzo#337, fix pichillilorenzo#341

added HeadlessInAppWebView class, added close, addMenuItem and addMen…

…uItems methods to ChromeSafariBrowser, added ChromeSafariBrowserMenuItem class, fixed InAppWebView.channel null exception on android, fix pichillilorenzo#305, fix pichillilorenzo#245, fix pichillilorenzo#299

updated pubspec.yaml