Update Buble to v20

[jasonwilliams]

buble v0.20 has less dependencies than v0.19.
I was getting warnings from old deps that Buble was bringing in but they've been removed in v20.

https://github.com/bublejs/buble/blob/master/CHANGELOG.md#0200-2020-03-26

[sapegin]

Feel free to send a pull request with a fix! 👾

[styleguidist-bot]

🎉 This issue has been resolved in version 11.0.9 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀