lint: Comma dangle

.eslintrc.js

@@ -55,6 +55,7 @@ module.exports = {
         'quotes': ['error', 'single'],
         'semi': ['error', 'always'],
         'indent': ['error', 4, { SwitchCase: 1, FunctionDeclaration: { parameters: 'first' } }],
+        'comma-dangle': ['error', 'always-multiline'],
 
         // These rules should eventually be enabled.
         'no-async-promise-executor': 'off',