Adds drop-in support for Dark mode

• Adds #40 thanks @yne

• New colors, thanks @yne #37
• Add .is-rounded, .is-pointer and .hide-pr, thanks @yne #38
• Add .dropdown class (#29)
• Rename text utility classes:
  text-center, text-left, text-right, text-uppercase, text-lowercase, text-capitalize
• Fix #36

• Fixes button group margins #33
• Add responsive helper #34

• Add device based grid #15
• Add util classes for border and viewport based visibility

See docs for more info.

• New .row.reverse
• fixes

• Full-width tabs #18
• Make outlined buttons the same size as their non-outlined counterpart #20

• Fixes #16, thanks #17

This release includes a major renaming of variables and a bunch of new variables.

• Error-success states
• Striped tables
• Button upgrades
• Enhancements to colors and styles
• New utilities & text styles