Scrollable performance refactor

[yairEO]

Performance improvements:

• Removed isEqual from updateScrollbars and replaced with a much faster check.
• Wrapped the DOM update-part with requestAnimationFrame
• Added optional prop cssVarsOnTracks which should be used when scrollable DOM content has a huge amount of DOM nodes, so the CSS variables will be applied to the scrollbars only and not the parent

see bug: bugs.chromium.org/p/chromium/issues/detail?id=1266517

[codecov[bot]]

Codecov Report

Merging #70 (cbbb465) into master (cf0e9e8) will increase coverage by 0.04%. The diff coverage is 93.93%.

@@            Coverage Diff             @@
##           master      #70      +/-   ##
==========================================
+ Coverage   95.39%   95.44%   +0.04%     
==========================================
  Files          61       61              
  Lines         847      856       +9     
  Branches       27       29       +2     
==========================================
+ Hits          808      817       +9     
  Misses         33       33              
  Partials        6        6              

Impacted Files	Coverage Δ
src/components/Scrollable/Scrollable.jsx	95.31% <92.00%> (+0.39%)	:arrow_up:
...onents/HorizontalScrollbar/HorizontalScrollbar.jsx	94.11% <100.00%> (+0.78%)	:arrow_up:
...components/VerticalScrollbar/VerticalScrollbar.jsx	94.11% <100.00%> (+0.78%)	:arrow_up:

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[ykadosh]

Don't forget to use the string fix() in one of your commits to trigger a release. Also, we need a PR in webrix-docs with the updated version and documentation updates if applicable.

[yairEO]

@ykadosh - if I put a fix in my commit, does Github knows my user have the permissions to trigger a build?

Thanks for reminding me to also make a PR in webrix-docs which documents this fix.

Initially I thought not documenting this change because it is something which was done specifically for Amdocs needs and requires an optional prop to <Scrollable cssVarsOnTracks={true}>, hoping Google will fix their bug this year:

https://bugs.chromium.org/p/chromium/issues/detail?id=1266517

It took some time to find a good-enough name for this prop

[ykadosh]

@yairEO the fix() commit message will only trigger a build once the PR is merged to master, so you don't have to worry about permissions. You can have as many fix() commits as you'd like, and it will only create a single patch version for all of them.

Regarding the documentation - i'm OK with not documenting this, as long as the default behavior is maintained (i.e. CSS variables on the parent by default). But you will need to create a PR there anyway, for updating the version in the package (which updates the version in the site header too).