Add json linter

This is intended to catch conflict markers in package*.json files,
which npm ignores. It also caught a duplicate key in one of the
fixture response objects.

Author: ugexe

.eslintrc.js

@@ -34,6 +34,17 @@ module.exports = {
       "rules": {
         "@typescript-eslint/await-thenable": "error",
       }
+    },
+    {
+      "plugins": [
+          "json"
+      ],
+      "files": [
+        "*.json",
+      ],
+      "rules": {
+          "json/*": ["error"]
+      }
     }
   ],
   "parserOptions": {

fixtures/insights.json

@@ -136,7 +136,6 @@
           "autonomous_system_organization": "Linkem IR WiMax Network",
           "connection_type": "Cable/DSL",
           "domain": "example.com",
-          "ip_address": "1.2.3.4",
           "is_anonymous": true,
           "is_anonymous_proxy": true,
           "is_anonymous_vpn": true,