Fix compatibility with release-it v15

[bertdeblock]

This will probably fail on the Node v12 scenario.

Closes #203.

[RobbieTheWagner]

@bertdeblock have you tried this out and it works? Might use your branch here until this is merged.

[bertdeblock]

@rwwagner90 I used the --dry-run flag to manually test these changes, but I didn't do an actual release.
Everything went smooth when performing a dry run, so I don't expect any hiccups when doing a real release.
All tests were passing as well locally. If you do use this branch, feel free to ping me if you run into any issues.

[scalvert]

We should also add version 15 to the ci.yml's release-it version matrix.

[bertdeblock]

Thanks for finishing this @scalvert! I was on vacation.

[scalvert]

My pleasure, @bertdeblock! Hope your vacation was good!