Add controlled list of marking types

src/MDMarkingTypesSet.php

@@ -0,0 +1,23 @@
+<?PHP
+/**
+ * Contains a class for controlling the list of available marking types.
+ *
+ * @author Joshua Ramon Enslin <joshua@museum-digital.de>
+ */
+
+/**
+ * Class containing available marking types.
+ */
+class MDMarkingTypesSet {
+
+    const MARKING_TYPES = [
+        'signature',
+        'engraving',
+        'watermark',
+        'scratch',
+        'stamp',
+        'overprint',
+        'embossing'
+    ];
+
+}