The script is a small wrapper around the `ci-run-eslint` package from World/javascript, which is a generalized and improved version of the .gitlab-ci/run-eslint script from gnome-shell. It only requires `npm` to be available, so it simplifies running eslint locally quite a lot Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/408>