postmessage not available on iOS

Hello

I need to close cordova iab after login, and I would do this with post message from browser in app to hybrid app
I've done with this code:

```
function dLogin() {
var messageObj = {
status: 200,
error: false,
message: "test",
user: {
id: 1,
token: "ABCDEF"
}
};
var stringifiedMessageObj = JSON.stringify(messageObj);
window['webkit'].messageHandlers['cordova_iab'].postMessage(stringifiedMessageObj);
}
```

Android build: all works fine
iOS build: window['webkit'] is not defined. I've tried with:
- window.
- webkit.
- (window as any).webkit

what I'm wrong?

thanks in advance

Start with dLogin() in the issue body and reproduce the iOS build, checking whether window.webkit.messageHandlers.cordova_iab is exposed in the InAppBrowser page. Compare the documented iOS messaging path with the working Android behavior; done means the login page can send the message and close the Cordova InAppBrowser on iOS.

Written by the indexing model from the issue text.