"Auto scroll sticky ToC to content" has weird behavior on Firefox

[iBug]

Most modern browsers enable smooth scrolling by default, but Firefox doesn't seem to handle multiple elements scrolling concurrently well (main content and sticky ToC). So for now I'll limit this feature to Chromium-based browsers by adding if (!!window.chrome).

If anyone would like to help getting this work on Firefox, you can inspect the code in #3115.