Transformer for Jest

It would be nice to have a Jest transformer that uses tsup so that we don't have to create an additional separate build configuration for Jest using babel or ts-jest.

The issue names Jest and tsup but does not identify files, tests, or an entry point. First inspect the repository's existing build configuration and determine where a Jest transformer would fit; done means Jest can use tsup without a separate Babel or ts-jest configuration.

Written by the indexing model from the issue text.