feat: Update peer dependencies for react 17.x (okonet#48)

feat: Add onSync callback to ScrollSync (okonet#38)

* feat: Add onSync callback to ScrollSync

* 📝 update docs

chore: Move to GH actions from Travis CI (okonet#28)

feat: Allow ScrollSyncPane to belong to multiple groups

feat: Add enable prop to control sync behavior (okonet#18)

feat: Sync newly added panes (okonet#17)

fix: Update peer dependency to React 16 (okonet#16)

Closes okonet#15

feat: Add scroll sync groups (okonet#11)

* add groups to react-scroll-sync
* update docs

fix(build): Add prepublish script to generate build on CI

Fixes okonet#10

build: Use node 8 only for CI