Migrate to JSON i18n

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

Change-Id: Ied3a4c392cf2ea16c6e858a1baaf9790db95e1f4

i18n/bn.json

@@ -0,0 +1,17 @@
+{
+    "@metadata": {
+        "authors": [
+            "Bellayet",
+            "Wikitanvir"
+        ]
+    },
+    "contributionscores": "অনুদানের স্কোর",
+    "contributionscores-top": "(সর্বোচ্চ $1)",
+    "contributionscores-days": "গত {{PLURAL:$1|দিন|$1 দিন}}",
+    "contributionscores-allrevisions": "সকল সংস্করণ",
+    "contributionscores-score": "স্কোর",
+    "contributionscores-pages": "পাতা",
+    "contributionscores-changes": "পরিবর্তন",
+    "contributionscores-username": "ব্যবহারকারী নাম",
+    "contributionscores-invalidusername": "অগ্রহণযোগ্য ব্যবহারকারী নাম"
+}