[RRFC] Add automatically installed peer deps to `package.json`

Motivation

Currently, when I install a package with peer dependencies in npm 7, they will automatically be installed and added to the package-lock.json. I think those peer deps should also be added to package.json, mimicking someone manually installing them. It would be nice to see which packages are installed in my project, especially when they are at the top level, otherwise, it feels like too much magic is going on that I cannot see.

Example

Say I have a package named foo with the peer dependencies bar and baz. I have not added any other packages to my project. bar and baz will then be automatically installed at the top level by npm (7), but they will not be included in package.json. I want them to be included in package.json so I can get a good overview of the(top-level) packages installed.

How

Add the automatically installed peer dependencies to package.json.

Current Behaviour

Peer dependencies are "magically" installed in the project and I cannot trust the package.json file to show me all packages installed.

Desired Behaviour

Add the automatically installed peer dependencies to package.json.

Start by reviewing npm 7's automatic peer-dependency installation behavior and the discussion on this RFC. Define how automatically installed top-level peer dependencies should be represented in package.json, while preserving the package-lock.json behavior; the desired result is that package.json shows those installed packages explicitly.