iOS: Add support for custom InputAccesoryView

When using TextField with inputMethodHints set to Qt.ImhDigitsOnly on iOS, the numeric keyboard is correctly opened but it's missing the "done" button (and eventually a "discard" button). Is there a way to display them?

Please see:
https://stackoverflow.com/questions/584538/how-to-show-done-button-on-ios-number-pad-keyboard

and

https://developer.apple.com/documentation/uikit/uiresponder/1621119-inputaccessoryview

This must be supported as the native iOS framework supports this. This is too weird not to have a button to accept the text and dismiss the keyboard with "enter" or "done" or "next" etc.