WEB I18N GAP FIXED: “Writing-modes sideways values not implemented”

With the release of Safari 18.4 all major desktop browsers now interoperably support the sideways-lr and sideways-rl values of CSS writing-mode.

This means it's now possible to properly display horizontal scripts in vertical arrangements, such as table headings.

This is a significant step forward, and turns many cells green in the language matrix! See https://www.w3.org/TR/latn-gap/#issue11_writing_mode