fix: upgrade babel-preset-airbnb from 2.4.0 to 2.6.0

Snyk has created this PR to upgrade babel-preset-airbnb from 2.4.0 to 2.6.0.

See this package in npm:
https://www.npmjs.com/package/babel-preset-airbnb

See this project in Snyk:
https://app.snyk.io/org/jswheeler/project/4efc4402-7d87-41c0-b7a9-f49d87158ca4?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot