Expose yargs-parser

[coreyfarrell]

Would you be willing to have yargs re-expose yargs-parser? My hope is for nyc to be able to do something like const {Parser} = require('yargs/yargs'). This would have the benefit of guaranteeing that when nyc uses the exact same version of yargs-parser as yargs itself. It would also reduce the maintenance burden for packages like nyc, for example right now yargs-parser@16.1.0 is available but latest yargs uses yargs-parser@^15.0.0 so anyone who blindly upgrades (my CI passed so it's good) would cause two copies of yargs-parser to get installed.

[bcoe]

I think this is a good idea, want to submit a patch ... we're about to release a major, so it would be a good time to land this feature.