@material-ui/system 4.0.0-beta.2 on Node.js NPM

A big thanks to the 13 contributors who made this release possible!

This is a stability release preparing v4.

[Box] Add export to barrel (index.js) (#15602) @ljvanschie
[ButtonBase] Extend error message for invalid component prop (#15627) @eps1lon
[Select] Add to docs that options must be direct descendants (#15619) @bh1505
[SwipeableDrawer] Remove internal accesses in the tests (#15469) @joshwooding
[Tabs] scrollButtons have an empty button error in compliance tools (#15646) @elnikolinho
[useScrollTrigger] Enhance trigger, improve tests (#15634) @cvanem

[styles] Fix warning false positive (#15595) @oliviertassinari
[styles] Keep MuiThemeProvider for backward compatibility (#15650) @oliviertassinari

[docs] Add custom default props handler (#15473) @eps1lon
[docs] Add next page link (#15656) @mbrookes
[docs] Add QuintoAndar in the showcase (#15622) @oliviertassinari
[docs] Fix dead David DM badges in README (#15667) @mbrookes
[docs] Fix few grammar issues (#15643) @DDDDDanica
[docs] Fix plural spelling (#15613) @cvanem
[docs] Fix some dev-only warnings (#15640) @eps1lon
[docs] Fix the adapting makeStyles based on props example syntax (#15621) @devarsh
[docs] Improve installation instructions for running the docs locally (#15608) @andreawaxman
[docs] Improve v3 migration guide (#15615) @eps1lon
[docs] Link edit page button to github editor (#15659) @mbrookes
[docs] Miscellaneous polish (#15665) @eps1lon
[docs] Reorganize the structure (#15603) @mbrookes
[docs] Update the translations (#15653) @mbrookes

[core] Drop partial chrome 41 support (#15630) @eps1lon
[core] Optimize clsx usage (#15589) @merceyz
[core] Remove react-event-listener from function components (#15633) @joshwooding
[core] Upgrade the dev dependencies (#15590) @oliviertassinari