Support new yarn-v2 ways of handling node modules with "plug and play"

See https://yarnpkg.com/features/pnp#fixing-node_modules

> In this install mode (the default starting from Yarn 2.0), Yarn generates a single .pnp.cjs file instead of the usual node_modules folder containing copies of various packages. The .pnp.cjs file contains various maps: one linking package names and versions to their location on the disk and another one linking package names and versions to their list of dependencies. With these lookup tables, Yarn can instantly tell Node where to find any package it needs to access, as long as they are part of the dependency tree, and as long as this file is loaded within your environment (more on that in the next section).