[Idea] Plan to make pn more useful

[Simon-Laux]

• detect pnpm in scripts and call pn instead
  - I believe the biggest time saving potential is in nested/composited script. In my test I replaced pnpm with pn manually in one of my scripts and got from 11 seconds to around 6 seconds.
• Support the --filter option and running scripts recursively in a workspace #13 - especially needed in monorepos
• if no package.json is found it should recurse to parent directories and look for it there like pnpm does.
• Publish on npm for fast installation and possibly integrate into pnpm as optional dependencies Publish.. #63 (comment)