Add MDRequirementsSet to list commonly used requirements

src/MDRequirementsSet.php

@@ -0,0 +1,19 @@
+<?PHP
+/**
+ * Class containing requirements for museum-digital generally.
+ *
+ * @author Joshua Ramon Enslin <joshua@museum-digital.de>
+ */
+declare(strict_types = 1);
+
+/**
+ * Class containing requirements for museum-digital generally.
+ */
+final class MDRequirementsSet {
+
+    // Object images need to be at least 500 px wide
+    const MIN_OBJECT_IMAGE_WIDTH = 540;
+    // Object images need to be at least 500 px wide
+    const MIN_OBJECT_IMAGE_HEIGHT = 540;
+
+}