Bug 1956645 - Parse and serialize view-transition-class. r=view-transitions-reviewers,firefox-style-system-reviewers,emilio

Parse and serialize `view-transition-class: none | <custom-ident>+`.
This property will be used after we extend `<pt-name-selector>` to
`<pt-name-and-class-selector>` for named view transition pseudo-elements.
Will do this in Bug 1956646. Also, we will handle the class matching in
Bug 1964949.

Differential Revision: https://phabricator.services.mozilla.com/D249681

devtools/server/actors/animation-type-longhand.js

@@ -190,6 +190,7 @@ exports.ANIMATION_TYPE_FOR_LONGHANDS = [
       "-moz-user-input",
       "user-select",
       "vector-effect",
+      "view-transition-class",
       "view-transition-name",
       "visibility",
       "white-space-collapse",