- removes `will-change: auto;` which is a performance hack which should be avoided and is probably causing more harm than good here
- lowers swipe velocity to 0.4 to ensure the modal can be dismissed with the thumb
- uses JS CSS animate API to animate the backdrop opacity
- uses the height of the modal container to have more precise values when computing backdrop opacity
- animate the modal container instead of the wrapper
- removes a useless template-lint-disable directive
- simplify the closing animation
- various small code tweaks to limit indirection
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