I cant find info about the peerDependenciesMeta field in the package.json:

https://docs.npmjs.com/files/package.json

References

It was mentioned at the npm blog here:

https://blog.npmjs.org/post/186983646370/npm-cli-roadmap-summer-2019

New features likely to land on the 6.x branch:

Add support for the peerDependenciesMeta field. (#224)

Also here in the changelog:

https://github.com/npm/cli/releases/tag/v6.11.0

Also the release announcement:

https://npm.community/t/release-6-11-0/9572