Updating all out-of-date [dev]dependencies. The two major ones are eslint and prettier.

This also switches to eslint's flat config file format, which is always a "fun" exercise. On this occasion, because we're using StandardJS, I ran into this issue. And I guess there's some opensource clownery going on in that project where the current published version of eslint-config-standard is broken but there's some debate over governance or... something? I dunno, I spent way too much time trying to figure out what was broken, and then why it can't be fixed, and then why the project had to be forked, then trying to figure out how to get the fork of the project working here.

And if anyone from StandardJS or NeoStandard ends up reading this... I WANT THE LAST TWO HOURS OF MY LIFE BACK, PLEASE!