Respect the difference between "root directory" and "project root"

[simonwiles]

See https://v2.parceljs.org/features/module-resolution/.

Parcel resolves dependencies relative to the project root which is derived from (but not necessarily the same as) the root directory. The current resolution algorithm, copied from ABuffSeagull/eslint-import-resolver-parcel, resolves relative to the root directory, which could technically be incorrect, I think. Need to come up with a test case.