Yarn / NPM detection is not aware of workspaces

[njlr]

Femto should attempt to find the root workspace (if there is one) before deciding to use NPM or Yarn

[Zaid-Ajaj]

Hi there @njlr, Femto decides to use the closest package.json file it can find, is there a way to automatically detect that a package JSON file is part of a workspace or should we add something like a --workspace <name> argument?

In any case, a PR would be much appreciated 🙏