Mark .ember-cli as jsonc instead of json

The .ember-cli file generated by Ember is JSON with Comments (jsonc): https://github.com/ember-cli/ember-cli/blob/master/blueprints/app/files/.ember-cli

I've changed its associated language accordingly because it being the JSON type by default causes red underlines in the generated file.

extensions/json/package.json

@@ -33,8 +33,7 @@
         ],
         "filenames": [
           "composer.lock",
-          ".watchmanconfig",
-          ".ember-cli"
+          ".watchmanconfig"
         ],
         "mimetypes": [
           "application/json",
@@ -57,6 +56,9 @@
           ".hintrc",
           ".babelrc"
         ],
+        "filenames": [
+          ".ember-cli"
+        ],
         "configuration": "./language-configuration.json"
       }
     ],