Both the .json and .yml config formats are deprecated in favor
of flat configs exported from eslint.config.js files.
The good news is that gjs' config is now available as a shared
config from the `eslint-config-gnome` package in World/javascript,
so we no longer have to copy the entire thing.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/merge_requests/408>
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>