Add RuleContainer interface for RuleSet and DeclarationBlock

Author: JakeQZ

config/phpstan-baseline.neon

@@ -54,12 +54,6 @@ parameters:
 			count: 1
 			path: ../src/RuleSet/DeclarationBlock.php
 
-		-
-			message: '#^Parameters should have "string\|null" types as the only types passed to this method$#'
-			identifier: typePerfect.narrowPublicClassMethodParamType
-			count: 2
-			path: ../src/RuleSet/DeclarationBlock.php
-
 		-
 			message: '#^Loose comparison via "\!\=" is not allowed\.$#'
 			identifier: notEqual.notAllowed

src/RuleSet/DeclarationBlock.php

@@ -30,7 +30,7 @@
  *
  * Note that `CSSListItem` extends both `Commentable` and `Renderable`, so those interfaces must also be implemented.
  */
-class DeclarationBlock implements CSSElement, CSSListItem, Positionable
+class DeclarationBlock implements CSSElement, CSSListItem, Positionable, RuleContainer
 {
     use CommentContainer;
     use Position;