Fix a regression with running jshint.
Review Request #12432 — Created July 1, 2022 and discarded
Review Bot 3 introduced a new jshint implementation that made use of a helper file to output as JSON. Unfortunately, the helper file did not ship with the package, due to the lack of `include_package_data=True` in the package configuration and the lack of a `MANIFEST.in` file. This fixes the packaging, ensuring we now ship the missing file.
Built packages and verified that the helper script, and other files from our source tree, were in the resulting wheel and source distributions.