* DragTarget part 1.
[WIP] Change GestureRecognizer. Sorry.
[WIP] Move from GestureRecognizer to MultiDragGestureRecognizer.
Make it a `Set<int>?`
Get bitwise operations working.
Fix test. Rename to allowedInputPointers.
Convert into a builder.
Improve code with default funciton.
Refactor everything again.
Rename to buttonEventFilter.
Use static function.
Fix analyzer.
Fix private reference.
Use // in private method.
* Fix Renzo request.
* Add `allowedButtonsFilter` everywhere.
* Refactor monoDrag for multi pointer support.
* Fix tests?
* Change default to always true.
* Fix PR comments.
* Completely refactor long press.
* Add forgotten class.
* Revert "Completely refactor long press."
This reverts commit 5038e8603e250e8c928b0f1754fb794b7b75738b.
* Add default value to LongPress
* Refactor doubleTap.
* Relax double tap.
* Write comment in LongPress.
* Use template.