pluraliser ignores selected words e,g, "staff"

src/Pluraliser.php

@@ -2,8 +2,14 @@
 
 namespace Drupal\opencase;
 
+
 class Pluraliser {
+    const NO_CHANGE = ['Staff'];
     public static function pluralise($text) {
-        return $text . "s";
+        if (in_array($text, self::NO_CHANGE)) {
+            return $text;
+        } else {
+            return $text . "s";
+        }
     }
 }