[Feature]: add velocity to onVerticalPull for Gallery

[janpe]

Summary

I'd like to implement a "pull to close" feature for Gallery. I'm able to do this now but I'd like to take the velocity of the gesture into consideration. So if the user pulls slowly all the way down and releases the Gallery will stay open. But if the user pulls quickly even if the translateY value is small at the point of release I'd like to close the Gallery.

Expected API

onVerticalPull: ({translateY: number, released: boolean, velocity: number}) => void

[Glazzes]

@janpe Sounds like a good idea, I'll add it right now.