Forgot to add pluraliser class (new file)

src/Pluraliser.php

@@ -0,0 +1,9 @@
+<?php declare(strict_types=1);
+
+namespace Drupal\opencase;
+
+class Pluraliser {
+    public static function pluralise($text) {
+        return $text . "s";
+    }
+}