Homepage (and docs) a bit hard to read on Firefox on Windows 8

I’ve tested on three different systems (all Windows 8), Firefox 78esr and 84, same result. It renders fine on Edge on the same system. Also tested on Firefox/Windows 10 and it’s fine there as well.

I don’t have the font (Bitter Thin) locally and Firefox shows it’s using the webfont Bitter-Roman.woff2 as it should be.