fix: List optional peer dependencies

[eps1lon]

Listing packages mentioned in https://github.com/websockets/ws#opt-in-for-performance-and-spec-compliance as optional peer dependencies.

Additional context:

• optional peer dependencies (implemented in yarn@1.13.0, npm@6.11.0 but not yet bundled with node and pnpm@?

I'm currently not using this feature myself until node bundles npm@6.11. Just creating this PR now so that we can discuss any concerns you have.

[lpinca]

Hmm, what happens wit yarn < 1.13.0 and npm < 6.11.0. I guess peerDependenciesMeta is just ignored right? So bufferutil and utf-8-validate would be treated as normal peer dependencies right?

[eps1lon]

So bufferutil and utf-8-validate would be treated as normal peer dependencies right?

Yep. For those package managers it would create warnings. However, this should be preferred over creating incomplete dependency trees.

[lpinca]

I think it makes more sense to add them as optionalDependencies if build failures do not cause installation to fail as per description. See discussion in #1220.

[lpinca]

The main difference is that peer dependencies are not installed by default which is nice. I like optional peer dependencies. The only thing I don't like is the warning that is raised with older versions of npm/yarn.

[eps1lon]

Yeah I can't help you with deciding what strategy to use since I only encountered this package as a transitive dependency.

The only thing I don't like is the warning that is raised with older versions of npm/yarn.

Heard this fairly often but IMO I'd rather have a warning (with a fix by upgrading the package manager) that does no harm instead of a dependency tree that is potentially broken. Especially with the amount of dependencies in the JS ecosystem you do not want to debug your dependency tree ever. That's what package managers are for but they require information from the packages.

[lpinca]

I'll wait until npm@6.11 is bundled in Node.js 10.

[lpinca]

Thank you.