ruler: Added storage of a timeline interval
Currently users are not able to create intervals on the timeline and developers are not able to attach any features relating to selecting an interval of the timeline.
Users would like to be able to select the timeline and developers for new features would like an easy way to access that interval.
We added new keybindings to i and o for our users to set the in and outpoints of the interval. It is stored within ruler.py in the ScaleRuler and can be accessed by calling get_interval.