Migrate to JSON i18n

Procedure per https://www.mediawiki.org/wiki/Manual:GenerateJsonI18n.php
with shim.

Change-Id: Ied3a4c392cf2ea16c6e858a1baaf9790db95e1f4

i18n/gv.json

@@ -0,0 +1,10 @@
+{
+    "@metadata": {
+        "authors": [
+            "MacTire02"
+        ]
+    },
+    "contributionscores-score": "Skensh",
+    "contributionscores-pages": "Duillagyn",
+    "contributionscores-username": "Ennym yn ymmydeyr"
+}