[feature request]: unresolvePath functionality

[zeorin]

It'd be great if this package could export an unresolvePath function alongside the resolvePath function, which does the exact opposite.

This would be great for projects like https://github.com/HeroProtagonist/eslint-plugin-module-resolver and https://github.com/Galooshi/import-js (see HeroProtagonist/eslint-plugin-module-resolver#1 and Galooshi/import-js#522).

This would help this plugin become more interoperable with the rest of the ecosystem, because if this plugin exposes the operation to resolve and unresolve, other software can count on this plugin to reliably reverse its operation. They'd all be using the same implementation of the unresolve functionality, and if you added some new way to resolve modules, those tools would automatically be able to use the unresolve function to unresolve them, without having to keep up to date themselves.