[TASK] Add native type declarations for RuleValueList (#1203)

Part of #811

Author: oliverklee

CHANGELOG.md

@@ -35,7 +35,7 @@ Please also have a look at our
   (#641, #772, #774, #778, #804, #841, #873, #875, #891, #922, #923, #933, #958,
   #964, #967, #1000, #1044, #1134, #1136, #1137, #1139, #1140, #1141, #1145,
   #1162, #1163, #1166, #1172, #1174, #1178, #1179, #1181, #1183, #1184, #1186,
-  #1187, #1190, #1192, #1193)
+  #1187, #1190, #1192, #1193, #1203)
 - Add visibility to all class/interface constants (#469)
 
 ### Deprecated

src/Value/RuleValueList.php

@@ -15,7 +15,7 @@ class RuleValueList extends ValueList
      * @param non-empty-string $separator
      * @param int<0, max> $lineNumber
      */
-    public function __construct($separator = ',', int $lineNumber = 0)
+    public function __construct(string $separator = ',', int $lineNumber = 0)
     {
         parent::__construct([], $separator, $lineNumber);
     }