Several feature requests: replay, frame by frame control

[designlook]

Replay

• When animation finishes playing and I trigger the play(), it does not play. Would be great if there is a replay method that restart it from beginning anytime it is trigger.

Frame-by-frame control

• Would be great depending on duration that it could figure out the number of frames and gives me indexes for all frames and I could go to any of them individually. Such as if I have a slider UI and can use it to scroll through the frames.