Added missing field 'headers' which returned by WebResourceResponse.toMap()

Upgraded appcompat to 1.2.0-rc-02

Use PlatformViewLink widget for Android WebView

Added missing `contextMenu` and `windowId` creation params for Android Hybrid Composition

Add AndroidInAppWebViewOption for using Hybrid Composition

This should solve issue with appcompat webview reported here: https://issuetracker.google.com/issues/141132133

Fixed iOS userContentController didReceive WKScriptMessage event when using a WebView created with a windowId

Reverted calling handler.post on Android when a WebView is created, Fixed iOS extra bottom padding when opening the keyboard, fix #429

added disableDefaultErrorPage Android-specific webview option, updated onCreateWindow event implementation

Updated onCreateWindow, onJsAlert, onJsConfirm, and onJsPrompt webview events, added onCloseWindow, onTitleChanged, onWindowFocus, and onWindowBlur webview events, added androidOnRequestFocus, androidOnReceivedIcon, androidOnReceivedTouchIconUrl, androidOnJsBeforeUnload, and androidOnReceivedLoginRequest Android-specific webview events, fix #403

Update README.md, Update missing docs, Fix pub.dev Health suggestions and Analysis suggestions, v3.4.0+1

Fixed HttpAuthCredentialDatabase.removeHttpAuthCredential on Android, Fixed some cases where takeScreenshot was not working on Android, fix #390, Updated HttpAuthCredentialDatabase.getAllAuthCredentials method return type