:octocat: move QRMarkupHTML::getCssClass() to QRMarkup abstract

src/Output/QRMarkup.php

@@ -82,7 +82,9 @@ abstract class QRMarkup extends QROutputAbstract{
 	/**
 	 * returns a string with all css classes for the current element
 	 */
-	abstract protected function getCssClass(int $M_TYPE):string;
+	protected function getCssClass(int $M_TYPE):string{
+		return $this->options->cssClass;
+	}
 
 	/**
 	 *

src/Output/QRMarkupHTML.php

@@ -50,11 +50,4 @@ class QRMarkupHTML extends QRMarkup{
 		return $html;
 	}
 
-	/**
-	 * @inheritDoc
-	 */
-	protected function getCssClass(int $M_TYPE):string{
-		return $this->options->cssClass;
-	}
-
 }