Font smoothing in MacOS looks bad

apparently on MacOS the fonts look very blurry in Firefox.

See https://pleroma.otter.sh/notice/9jdXlH2sLWG8QKZWdc and https://pleroma.otter.sh/notice/9jdXRfhEz61P5O6ajQ. Solution seems to be to add -moz-osx-font-smoothing: grayscale; to the body.