text-transform property supports the value "full-size-kana" https://drafts.csswg.org/css-text-3/#valdef-text-transform-full-size-kana https://wpt.fyi/results/css/css-text/text-transform?label=master&label=experimental&aligned&view=subtest&q=full-size-kana https://drafts.csswg.org/css-text-3/#small-kana
<rdar://problem/105181094>
Gecko has an implementation: https://bugzilla.mozilla.org/show_bug.cgi?id=1498148
Pull request: https://github.com/WebKit/WebKit/pull/9931
Committed 260307@main (8ca11a6d7868): <https://commits.webkit.org/260307@main> Reviewed commits have been landed. Closing PR #9931 and removing active labels.