normalize babel syntax transforms with other public CTF libs

[axe312ger]

This will make sure the core, CDA and CMA libs all support the very same browsers and node versions.

Partner PRs:

• https://github.com/contentful/contentful.js/pull/2158
• https://github.com/contentful/contentful-management.js/pull/2176

[contentful-automation[bot]]

:tada: This PR is included in version 8.1.3 :tada:

The release is available on:

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

Your semantic-release bot :package::rocket: