[String] Add PLURAL_MAP "zombies" -- fix #43789

The word "zombies" should be singularized to "zombie" (rather than
"zomby"). We provide a PLURAL_MAP for this case, as well as a test.

Author: acodispo

Inflector/EnglishInflector.php

@@ -58,6 +58,9 @@ final class EnglishInflector implements InflectorInterface
         // selfies (selfie)
         ['seifles', 7, true, true, 'selfie'],
 
+        // zombies (zombie)
+        ['seibmoz', 7, true, true, 'zombie'],
+
         // movies (movie)
         ['seivom', 6, true, true, 'movie'],
 

Tests/Inflector/EnglishInflectorTest.php

@@ -152,6 +152,7 @@ public function singularizeProvider()
             ['trees', 'tree'],
             ['waltzes', ['waltz', 'waltze']],
             ['wives', 'wife'],
+            ['zombies', 'zombie'],
 
             // test casing: if the first letter was uppercase, it should remain so
             ['Men', 'Man'],