If a package requires a certain engine or Node version to run, pnpm should

• skip it if the dependency is optional
• print a warning if engine-strict is false
• fail if engine-strict is true

This package might help in implementation: https://github.com/npm/npm-install-checks

This is where npm does the check: https://github.com/npm/npm/blob/d081cc6c8d73f2aa698aab36605377c95e916224/lib/install/validate-args.js