Error using the package when testing with Vitest

[Martin Domajnko]

Hi @developit. This package is one of our sub dependencies and is causing the following issue when testing with Vitest:

I managed to patch and resolve the issue in our project, but it would be nice if the original code can get fixed, so I will open a PR.

The PR will add TSUP to bundle, which simplifies the bundling process and I also fixed the package.json exports to match the changes.

I tested the newly bundled package on arethetypeswrong and it looks like its packaged fine to support both ESM and CJS environments.