Add script variants for Serbo-Croatian (sh-cyrl and sh-latn)

Script variants for Serbo-Croatian have been added to Names.php [1] as part of
the changes for adding a language converter [2].

[1] a573bea01b/includes/languages/data/Names.php (422)
[2] https://phabricator.wikimedia.org/T268033

data/language-data.json

@@ -3986,6 +3986,16 @@
             ],
             "srpskohrvatski"
         ],
+        "sh-cyrl": [
+            "Cyrl",
+            [
+                "EU"
+            ],
+            "српскохрватски"
+        ],
+        "sh-latn": [
+            "sh"
+        ],
         "shi-latn": [
             "Latn",
             [