https://www.w3.org/TR/2003/WD-css3-content-20030514/#wrapping describes how the ::outside pseudo-element would work. Note that this draft is very old and the idea has been abandonned in the meantime, but I don't see a problem with implementing it anyway.
https://www.w3.org/TR/2003/WD-css3-content-20030514/#wrapping describes how the
::outsidepseudo-element would work. Note that this draft is very old and the idea has been abandonned in the meantime, but I don't see a problem with implementing it anyway.See also https://github.com/braillespecs/braille-css/issues/33.