fix: switch babel-plugin-macros to a peer dependency (again)

[JoshuaKGoldberg]

PR Checklist

• [x] Addresses an existing open issue: fixes #88
• [x] That issue was marked as status: accepting prs
• [x] Steps in CONTRIBUTING.md were taken

Overview

Re-applies #60 per the issue.

[github-actions[bot]]

:tada: This is included in version v1.5.2 :tada:

The release is available on:

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

Cheers! 📦🚀