NPM/PNPM: Add support for peer dependencies

[mnonnenmacher]

Add support for the peerDependencies scope to NPM. Be aware that the specific version of the peer dependency will only be resolved in the context of a project using the library.

npm-install-peers can be used to install peer dependencies, see this relevant ticket:
spatie/npm-install-peers#13

[tsteenbe]

@mnonnenmacher Harp.gl has multiple peer dependency on three.js see https://github.com/heremaps/harp.gl/blob/e3110f1dc35a889059ba23faefc76e3a4c1cfe73/%40here/harp-debug-datasource/package.json#L42

Now ORT does not pick up the core library that powers harp.gl

[sschuberth]

Good write-up about what peer dependencies actually are: https://nodejs.org/en/blog/npm/peer-dependencies/. Basically, peer dependencies define against what API of a "host" package a (plugin) package has been written.

A problem is that different NPM versions behave differently WRT to peer dependencies, quoting the article:

UPDATE: npm versions 1, 2, and 7 will automatically install peerDependencies if they are not explicitly depended upon higher in the dependency tree. For npm versions 3 through 6, you will receive a warning that the peerDependency is not installed instead.