PNpM CLI

Minor Changes

• pnpm import can convert a yarn.lock to a pnpm-lock.yaml #3655.
• Backward-compatible change to the lockfile format. Optional dependencies will always have the requiresBuild field set to true. This change is needed to allow skipping optional dependency downloads, when the optional dependency is not compatible with the target system #2038

Patch Changes

• Those optional dependencies that don't support the target system should not be downloaded from the registry #2038.
• Don't crash on unsupported packages that are only dependencies of skipped optional dependencies #3640.
• Allow to symlink a directory that has no package.json #3691.