feat: ensure regenerator-runtime is available (for WP 6.6)

[dkoo]

All Submissions:

• [x] Have you followed the Newspack Contributing guideline?
• [x] Does your code follow the WordPress' coding standards and VIP Go coding standards?
• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

WP 6.6 changes some things and regenerator-runtime is not available anymore. This PR adds it to every entry file processed by webpack.

How to test the changes in this Pull Request:

No functional changes—all should work as expected.

* 6.6-beta2 to be exact

Other information:

• [x] Have you added an explanation of what your changes do and why you'd like us to include them?
• [ ] Have you written new tests for your changes, as applicable?
• [x] Have you successfully ran tests with your changes locally?

[matticbot]

:tada: This PR is included in version 4.4.0-alpha.3 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket:

[matticbot]

:tada: This PR is included in version 4.4.0 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket: