[TASK] Add native type declarations for Charset

CHANGELOG.md

@@ -34,7 +34,7 @@ Please also have a look at our
 - Use more native type declarations and strict mode
   (#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)
+  #1162, #1163, #1166, #1172, #1174, #1178)
 - Add visibility to all class/interface constants (#469)
 
 ### Deprecated

config/phpstan-baseline.neon

@@ -54,12 +54,6 @@ parameters:
 			count: 1
 			path: ../src/Property/CSSNamespace.php
 
-		-
-			message: '#^Method Sabberworm\\CSS\\Property\\Charset\:\:atRuleArgs\(\) should return string but returns Sabberworm\\CSS\\Value\\CSSString\.$#'
-			identifier: return.type
-			count: 1
-			path: ../src/Property/Charset.php
-
 		-
 			message: '#^Only booleans are allowed in an if condition, Sabberworm\\CSS\\Value\\RuleValueList\|string\|null given\.$#'
 			identifier: if.condNotBoolean

src/Property/Charset.php

@@ -63,10 +63,7 @@ public function setCharset($charset): void
         $this->charset = $charset;
     }
 
-    /**
-     * @return string
-     */
-    public function getCharset()
+    public function getCharset(): string
     {
         return $this->charset->getString();
     }
@@ -92,10 +89,7 @@ public function atRuleName(): string
         return 'charset';
     }
 
-    /**
-     * @return string
-     */
-    public function atRuleArgs()
+    public function atRuleArgs(): CSSString
     {
         return $this->charset;
     }