Use rollup instead of webpack

[RobbieTheWagner]

Todo:

• Get Stylelint working again
• Fix coverage calculations and ignore files we don't care about
• Explore using multiple output entries to output cjs, esm, umd, etc. and set the corresponding package.json fields for main, browser, module etc
• Use plain css for docs styles
• Figure out why styles/transitions are buggy when clicking next/previous in tours. Seems something is wrong with the output somewhere.

[chuckcarpenter]

This LGTM, but what were the reasons again for moving to Jest?

[RobbieTheWagner]

@chuckcarpenter moving to Jest was mostly just because it kind of handles everything out of the box. We had a lot of custom stuff to get mocha running, and Jest just needs to run jest