Merge pull request smooth-code#42 from smooth-code/tree-shaking

perf: improve tree shaking

Merge pull request smooth-code#41 from smooth-code/prefers-reduce-motion

feat(a11y): support "prefers-reduce-motion"

refactor: use core-em instead of core-emotion

fix(Row): fix default gutter

Merge pull request smooth-code#22 from smooth-code/factorize-code

Factorize code

fix(modal): fix modal backdrop (smooth-code#19)

chore: fix rollup

Merge pull request smooth-code#14 from smooth-code/fix-modals

fix(modal): fix default opened

feat: add Button default variant (primary)

Merge pull request smooth-code#11 from smooth-code/fix-build

fix: fix import X from 'smooth-ui/X'