LibWeb: Support CSS font-optical-sizing property

Author: https://github.com/Calme1709
Commit: https://github.com/LadybirdBrowser/ladybird/commit/11d524bda4c
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/7666
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/CSS/Properties.json

@@ -1850,7 +1850,7 @@
   },
   "font": {
     "initial": "normal medium serif",
-    "__comment": "FIXME: Support font-optical-sizing and font-size-adjust as reset-only sub-properties",
+    "__comment": "FIXME: Support font-size-adjust as a reset-only sub-property",
     "longhands": [
       "font-family",
       "font-size",
@@ -1862,6 +1862,7 @@
       "font-feature-settings",
       "font-kerning",
       "font-language-override",
+      "font-optical-sizing",
       "font-variation-settings"
     ]
   },
@@ -1909,6 +1910,14 @@
       "normal"
     ]
   },
+  "font-optical-sizing": {
+    "animation-type": "discrete",
+    "inherited": true,
+    "initial": "auto",
+    "valid-types": [
+      "font-optical-sizing"
+    ]
+  },
   "font-size": {
     "animation-type": "by-computed-value",
     "inherited": true,