tools: enable ES2016 syntax support in ESLint

This allows us to use the exponentiation operator.

PR-URL: #9218
Ref: #9208 (comment)
Reviewed-By: Teddy Katz <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>

Author: targos

.eslintrc

@@ -2,6 +2,9 @@ env:
   node: true
   es6: true
 
+parserOptions:
+  ecmaVersion: 2016
+
 rules:
   # Possible Errors
   # http://eslint.org/docs/rules/#possible-errors