Lint JSON files with ArcanistJSONLinter.

Summary: After D9628, we can lint JSON files natively.

Test Plan: See D9652.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9654

Author: joshuaspence

.arclint

@@ -28,6 +28,15 @@
       ],
       "jshint.jshintrc": "support/jshint/jshintconfig"
     },
+    "json": {
+      "type": "json",
+      "include": [
+        "(^support/jshint/jshintconfig$)",
+        "(^\\.arcconfig$)",
+        "(^\\.arclint$)",
+        "(\\.json$)"
+      ]
+    },
     "generated": {
       "type": "generated"
     },