Stop Progress Bar's Animation Smoothly

[ShahriarKh]

It will be better if the progress bar stops smoothly, instead of a sudden stop.
I tried looking at the source code to do it by myself, but found out that progress bar animation is using animation-play-state and there's no timing function (& thus no ease-in, ease-out) for it.
I also asked about this in StackOverflow so we might find a better solution.
https://stackoverflow.com/questions/70428394/how-to-use-timing-functions-with-animation-play-state

I'd really like to contribute, so any help is appreciated!