[internal] upgrade to babel@7

[hshoff]

This PR upgrades vx packages to use babel 7. babel-upgrade does most of the heavy lifting. A huge help for a monorepo.

Thanks to @skevy for pointing out how painless the migration is which motivated me to do it.

Runbook

For each package:

1. npx babel-upgrade --write info
2. remove external-helpers from rollup.config.js rollup-plugin-babel for babel 7 now dedups helpers
3. update build:babel cmd to babel 7 plugins
4. update rollup version to 0.67.4
5. rm -rf ./node_modules
6. npm install
7. npm run test

Testing

• all tests pass
• run vx-demo.now.sh/gallery locally with no errors

Changelog

📝 Documentation

• [gallery] add <BarStackHorizontal /> example code back

🏠 Internal

• [internal] upgrade to babel@7

[williaster]

woot! nice 👌 I did this for @data-ui recently and it was a bit painful ... mostly beemo learning curve. glad babel-upgrade made it easier!