Proposal for ludicrous speed

The idea is to symlink packages to a shared location, including a node_modules symlink that allows the call site to specify the dependencies.

Absurdly fast install times, and excellent monorepo support.

This is the submission in the yarn RFC process: https://github.com/yarnpkg/rfcs/pull/119/commits/0eff527aa4f92b9c8595a093e1845a6720cc842e?short_path=cd9ed55#diff-cd9ed55adb33286af163c26015785a21