Implement parser for @font-face size-adjust descriptor according to https://www.w3.org/TR/css-fonts-5/#size-adjust-desc
Pull request: https://github.com/WebKit/WebKit/pull/13020
Committed 263248@main (2148febf9f0e): <https://commits.webkit.org/263248@main> Reviewed commits have been landed. Closing PR #13020 and removing active labels.