Fix es2020 globals not being recognized

Fixes standard/standard#1436

The ecmaVersion in parserOptions is only for setting syntax support.

From the docs: https://eslint.org/docs/user-guide/configuring

> supporting ES6 syntax is not the same as supporting new ES6 globals

Setting the es2020 env will actually set the globals:

> adds all ECMAScript 2020 globals and automatically sets the ecmaVersion parser option to 11.

Author: faridnsh

eslintrc.json

@@ -8,7 +8,7 @@
   },
 
   "env": {
-    "es6": true,
+    "es2020": true,
     "node": true
   },