Scroll background on safari ios 11.4

[vitqst]

Issue : thanks for your awesome library, i have 1 issue on ios 11.4 ( iphone X ), modal opened so when we scroll time on body content background still scrollable

p/s : i edited your library for my project

[vitqst]

I fixed this bug

const style = document.body.style;
// when popup open
style.overflow = 'hidden';
style.position = 'fixed';
style.width = '100%';
// when popup close
style.overflow = 'auto';
style.position = '';