Intent to prototype & ship: CSS text-emphasis-position:auto

[Jonathan Kew]

Summary: Enables correct language-specific behavior for CSS
text-emphasis without the need for explicit :lang(..) rules in the
stylesheet

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1919658

Standard:
https://drafts.csswg.org/css-text-decor/#text-emphasis-position-property
(not yet updated for recent CSSWG resolution in
https://github.com/w3c/csswg-drafts/issues/1198#issuecomment-2358986319)

Standards Body: CSSWG (W3C)

Platforms: All

Preference: None, the new value is a minor addition with minimal risk of
breakage for existing content

DevTools bug: n/a

Other browsers: No support yet, but both webkit and blink
representatives were present in the WG discussion that resolved to add this

WPT: Test coverage added as part of bug 1919658

-- JK