LibWeb: Do broad invalidation when @function rule is added/removed

Author: Calme1709

Libraries/LibWeb/CSS/StyleSheetInvalidation.cpp

@@ -570,6 +570,7 @@ static bool rule_requires_broad_add_or_remove_invalidation(CSSRule const& rule)
     case CSSRule::Type::CounterStyle:
     case CSSRule::Type::LayerBlock:
     case CSSRule::Type::LayerStatement:
+    case CSSRule::Type::Function:
     // @font-feature-values changes how font-variant-alternates resolves at computed-style time, so
     // a declaration-time mutation still requires a whole-subtree restyle.
     case CSSRule::Type::FontFeatureValues:

Tests/LibWeb/Text/expected/wpt-import/css/css-mixins/function-invalidation.txt

@@ -2,9 +2,8 @@ Harness status: OK
 
 Found 4 tests
 
-1 Pass
-3 Fail
+4 Pass
 Pass	Appending a rule
-Fail	Prepending a rule
-Fail	Deleting a rule
-Fail	Prepending a rule, then deleting last
+Pass	Prepending a rule
+Pass	Deleting a rule
+Pass	Prepending a rule, then deleting last