Feature Request: TransformableBox should enable onTap Event Propagation to Child Widgets

[AndersKlint]

Is your feature request related to a problem? Please describe.
When tapping inside the box, I want the child to catch the onTap event. In my case I show the box over a camera feed which supports onTaps to focus the camera on that point. If I tap inside the box, the underlying camera feed should catch that event.

Describe the solution you'd like

• Either add shouldCaptureTapEvents parameter. True by default.
• include tapDetails in the onTap callback of TransformableBox.

Describe alternatives you've considered
Maybe there's a solution around this? I tried wrapping the Transformable box in a GestureDetector, but it throws an exception as it excepts to be a direct ancestor of a stack. Moving the detector to the TransformableBox's doesn't work either, as it seems the box catches the tap events.

[AndersKlint]

I was able to achieve this behaviour with a small fix and opened a PR:
#32