[CLEANUP] Change AtRule::BLOCK_RULES to an array (#1556)

Author: JakeQZ

src/CSSList/CSSList.php

@@ -222,7 +222,7 @@ private static function parseAtRule(ParserState $parserState): ?CSSListItem
                 }
             }
             $useRuleSet = true;
-            foreach (\explode('/', AtRule::BLOCK_RULES) as $blockRuleName) {
+            foreach (AtRule::BLOCK_RULES as $blockRuleName) {
                 if (self::identifierIs($identifier, $blockRuleName)) {
                     $useRuleSet = false;
                     break;

src/Property/AtRule.php

@@ -18,8 +18,17 @@ interface AtRule extends CSSListItem
      *
      * @internal since 8.5.2
      */
-    public const BLOCK_RULES =
-        'media/document/supports/region-style/font-feature-values/container/layer/scope/starting-style';
+    public const BLOCK_RULES = [
+        'media',
+        'document',
+        'supports',
+        'region-style',
+        'font-feature-values',
+        'container',
+        'layer',
+        'scope',
+        'starting-style',
+    ];
 
     /**
      * @return non-empty-string

tests/Unit/Property/AtRuleTest.php

@@ -29,7 +29,7 @@ public function blockRulesConstantIsCorrect(): void
                 'scope',
                 'starting-style',
             ],
-            explode('/', AtRule::BLOCK_RULES)
+            AtRule::BLOCK_RULES
         );
     }
 }