Added onHover and onTapCancel callbacks

[apalala-dev]

Touchable didn't provide onTapCancel and onHover callbacks, so I added them.
It can be used to interact better with the canvas on web & desktop.

An example for the onHover usage is to display a MouseRegion with a SystemMouseCursors.click when hovering clickable parts of a canvas.

On the other end, onTapCancel allows to disable more easily a pressed state when cancelling a tap on a Shape.

Example:

MouseRegion(
  cursor: _cursor ?? SystemMouseCursors.basic,
  child: CanvasTouchDetector(
    gesturesToOverride: const [
      GestureType.onTapDown,
      GestureType.onTapUp,
      GestureType.onHover,
      GestureType.onTapCancel,
    ],
    builder: (context) => CustomPaint(
      painter: MyCustomPainter(
        context,
        // other args
        onHover: (details) {
          if (details.hovering == true) {
            if (_cursor != SystemMouseCursors.click) {
              setState(() {
                _cursor = SystemMouseCursors.click;
              });
            }
          } else {
            if (_cursor != SystemMouseCursors.basic) {
              setState(() {
                _cursor = SystemMouseCursors.basic;
              });
            }
          }
        },
        onTapDown: (_) {
          // Do some stuff
          setState(() {
            _isPressing = true;
          });
        },
        onTapUp: (_) {
          setState(() {
            _isPressing = false;
          });
        },
        onTapCancel: () {
          setState(() {
            _isPressing = false;
          });
        },
      ),
    ),
  ),
);

And in MyCustomPainter's paint method:

var myCanvas = TouchyCanvas(context, canvas);
myCanvas.drawRRect(
      buttonRect,
      Paint()..color = isPressing ? Colors.blue : Colors.red,
      onTapDown: onTapDown,
      onTapUp: onTapUp,
      onTapCancel: onTapCancel,
      onHover: onHover,
    );

[nateshmbhat]

@apalala-dev thank you for your contribution ! :)
can u please give a description of the changes u've done and the reasons for the changes ?

there's a conflict in one file, please push a fix.

[apalala-dev]

I updated the description and merged the conflict :)

[darkomenx]

Is there possible to process a review for this pull request please ?
It is a very useful add for this package...