AudioPlayerViewController: Add double tap gesture to seek

This merge request brings an addition to the Audio Player gestures with:

• A double tap gesture to seek backwards/forwards depending on the location the users taps on the screen.

This merge request also introduces an extension that constructs a String object describing the duration that can represent the base Int object.

It is notably used when we build the message containing information about the total duration that the user skipped when performing the double tap gesture. It can also be used for other ways of seeking such as the swipe gesture.