By adding the `.js`-extension to the bin-file, IDEs will
know that js code-highlighting should be applied to the
file, which makes it easier for devs to read the code.
- adds full unit tests for all cli options
- demonstrates that nothing changes between minimist and yargs except a minor order change in the --help text
- proves b9c4b253e works the same as before
Co-authored-by: fabb <fabb@users.noreply.github.com>