Specify webpack as an optional peer dependency

[flying-sheep]

This is basically the same PR as vuejs/vue-loader#1853 + vuejs/vue-loader@089473a

See https://yarnpkg.com/configuration/yarnrc#packageExtensions on why this should be fixed here.

Fixes #449

[sindresorhus]

This is a Yarn issue and I'm simply not interested in working around all the Yarn bugs. Instead, try to get Yarn to fix it.

#449 (comment)

[flying-sheep]

I think you misunderstood: Yarn is just stricter about the semantics of peer dependencies.

I think if a package uses another package that has a peer dependency, it’s supposed to specify that dependency itself in some fashion. That’s what yarn points out here.

If you think this is a yarn bug, what’s the mistake yarn makes here in your opinion? Do you disagree with its interpretation of peer dependencies, or … ?

[fregante]

Not the place to discuss Yarn. There's also already an issue for related discussion, which is closed. If resolved, a solution could be applied. This PR doesn't work.