[CLEANUP] Refactor and enhance CSSString::escape() (#1467)

Fixes #1466

Author: oliverklee

src/Value/CSSString.php

@@ -93,9 +93,9 @@ public function getString(): string
      */
     public function render(OutputFormat $outputFormat): string
     {
-        $string = $this->escape($this->string, $outputFormat->getStringQuotingType());
-        $string = \str_replace("\n", '\\A', $string);
-        return $outputFormat->getStringQuotingType() . $string . $outputFormat->getStringQuotingType();
+        return $outputFormat->getStringQuotingType()
+            . $this->escape($this->string, $outputFormat)
+            . $outputFormat->getStringQuotingType();
     }
 
     /**
@@ -112,14 +112,14 @@ public function getArrayRepresentation(): array
         ];
     }
 
-    /**
-     * @param "'"|'"' $quote
-     */
-    private function escape(string $string, string $quote): string
+    private function escape(string $string, OutputFormat $outputFormat): string
     {
         $charactersToEscape = '\\';
-        $charactersToEscape .= ($quote === '"' ? '"' : "'");
+        $charactersToEscape .= ($outputFormat->getStringQuotingType() === '"' ? '"' : "'");
+        $withEscapedQuotes = \addcslashes($string, $charactersToEscape);
+
+        $withNewlineEncoded = \str_replace("\n", '\\A', $withEscapedQuotes);
 
-        return \addcslashes($string, $charactersToEscape);
+        return $withNewlineEncoded;
     }
 }