Add onTap to Notification Widget

[marioki]

This PR adds functionality to set an onTap Function to be called when the user taps anywhere on the notification Material Widget. New Parameters Added to ElegantNotification widget:

1. onTap Optional Parameter to set a Function to call when the notification is tapped.
2. dismissOnTap a boolean Flag to define wheater the notification should be dismissed when tapped (set to true by default).

Other Considerations:

• A notification can have an onTap, an action and a closeButton each with their corresponding Function call.
• added two new entries to the example app.

[koukibadr]

@marioki same updates as This PR the new updates will be available in the next published version

[marioki]

@koukibadr Have you considered allowing users to use actions + onTap? There's a use case where tapping the notification, for example, navigates to a particular route, while using an action performs a quick response. This PR allows for both to be used.

[koukibadr]

The latest published version contains onTap and closeOnTap attributes where:

• onTap a callback invoked when the user press the widget
• closeOnTap boolean indicate whether the notification get closed on pressing it or not