Optional core-js polyfill and change javascript utility from lodash to just

[sadeghbarati]

https://bundlephobia.com/package/smooth-scrollbar@8.7.0

optional core-js for the next release will be the best option because ppl may already have core-js polyfills on their project (duplicate polyfills code)
or even don't wanted to polyfill older browsers

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optional: use just utility instead of lodash

https://github.com/angus-c/just
https://github.com/puruvj/all-of-just
lodash vs just: angus-c/just#4

[idiotWu]

We are going to remove core-js in the next release 😆