Add onTap and closeOnTap methods

[ferraridamiano]

Hi there!
This PR adds a couple of useful properties to this package:

• onTap let the user click on the whole notification. A developer cannot set both an action and onTap
• closeOnTap is a property that if set to true closes the notification on user interaction (onTap or action pressed)

Thanks for this package, it is very useful. Now I only miss the swipe to remove gesture on the notification. Thanks for moving the packege to MIT license

[koukibadr]

According to the changes when closeOnTap == true but onTap is null the closeOnTap won't work properly (it won't close the popup)
I propose you update the InkWell widget as below

InkWell(
        onTap:() {
                widget.onTap?.call();
                if (widget.closeOnTap) {
                  closeNotification();
                }
              },

[ferraridamiano]

closeOnTap is meant to be only on user iteraction, i.e. only when onTap or an action are pressed. If there is no action or tap event associated with it, it should not close. What do you think about it?

[koukibadr]

closeOnTap is meant to be only on user iteraction, i.e. only when onTap or an action are pressed. If there is no action or tap event associated with it, it should not close. What do you think about it?

Let me test it first this evening and then we merge it and publish a new version