Docs: Add new ES environments to Configuring ESLint (#12289)

docs/user-guide/configuring.md

@@ -138,6 +138,8 @@ An environment defines global variables that are predefined. The available envir
 * `commonjs` - CommonJS global variables and CommonJS scoping (use this for browser-only code that uses Browserify/WebPack).
 * `shared-node-browser` - Globals common to both Node.js and Browser.
 * `es6` - enable all ECMAScript 6 features except for modules (this automatically sets the `ecmaVersion` parser option to 6).
+* `es2017` - adds all ECMAScript 2017 globals and automatically sets the `ecmaVersion` parser option to 8.
+* `es2020` - adds all ECMAScript 2020 globals and automatically sets the `ecmaVersion` parser option to 11.
 * `worker` - web workers global variables.
 * `amd` - defines `require()` and `define()` as global variables as per the [amd](https://github.com/amdjs/amdjs-api/wiki/AMD) spec.
 * `mocha` - adds all of the Mocha testing global variables.