fix: add file extension to import path to support Node16 and NodeNext module resolution

[frederikprijck]

Description

When using node16 or nodenext moduleresolution, tsc would throw errors. See #169

References

relative import paths need full extensions (e.g we have to write import "./foo.js" instead of import "./foo")

typescriptlang.org/docs/handbook/esm-node.html

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not the default branch

[frederikprijck]

Marking as draft until we got some feedback on #169

[jonkoops]

@frederikprijck I think we can close this one now that all the files that end up in the distribution are bundled (also the types). It would however be nice if we can default to Node16 for the TSConfig at some point, but I have already found several dependencies that have broken types under that mode, so I'll have to fix those upstream first.

[jonkoops]

@frederikprijck I think the branch for this PR can be deleted as well.