Fix transition animations

[xeophin]

The code supports now three different animation types:

• Scroll tracked (scrub video to match the scroll position)
• Video based, where the video plays at the original speed until it reaches the requested videoPercentage
• Time based, where the transition takes a fixed amount of time and the video is sped up or slowed down to fit within that time; with the option to modulate the speed using an easing function.

[xeophin]

Wait, Github tripped me up and made me create a pull request in the wrong repo. Sorry! 🤦🏻‍♂️

Slightly premature PR – you're welcome to ignore it. Or we can discuss whether it needs additional changes, if you're interested in the changes we made.

[dkaoster]

@xeophin no problem, thank you for doing this! I can find some time to look through this and collect some thoughts.