Created by: bardiharborow
In lieu of an official style guide, this takes the eslint:recommended preset, and then enables every ESLint rule that does not cause significant disruption to the codebase. It then disables the rules needed for js/tests to pass, as that follows a slightly different style. We may wish to tighten quite a bit of this later, but it's better than what we currently have.
This is one half of the fix for #20466 (closed), the other half being houndci/hound#889. This works towards #20740 (closed), but I suspect there is more to do, noting especially that ESLint does not cover all folders yet, as per #17924 (closed).