Layout insets

[moffatman]

You can provide layoutInsets on the image, this could be use to position outside of the notch, home indicator. But you can still zoom, and it will paint underneath those edges. It will let you scroll to the edge of the image, and you could drag the image outside of the notch to see all the details.

Fixes #417

Please note, to get Hero to work without any jumping, you might need to do something like the following, in case you have different layoutInsets on both widgets.

heroBuilderForSlidingPage: (Widget result) {
  return Hero(
    tag: _tag,
    child: result,
    flightShuttleBuilder: (ctx, animation, direction, from, to) => AnimatedBuilder(
      animation: animation,
      builder: (ctx, child) => Padding(
        padding: layoutInsets * animation.value,
        child: child
      ),
      child: from.widget
    )
  );
}

I don't think the above could be automatically done.