To keep up to date with our dependencies (#231, #228, #226, #222, #199) and to enable us to use modern JS features (#204 (comment)) I would suggest that we align with ESLint 9's engine range, ^18.18.0 || ^20.9.0 || >=21.1.0, for the next major release.

As I mention in #204 (comment), but haven't gotten any feedback on, I would like to address this issue before spending time on undoing modern JS to something old only to have us drop the old engines right afterwards.