cookbook: Add recipe about handling button events

cookbook: Add recipe about handling button events

Recipe covers adding handlers for button-press-event and
button-release-event signals on actors, and how to
examine the content of a ClutterButtonEvent via API functions.

The discussion section explains about click count
(the criteria for how clicks get counted, including
distance and time settings); how button numbers are reported;
and how to use ClutterClickAction as an alternative
for press + release in certain scenarios.