Support esx from eslint-config-frontier-react (#32)

esx is applied to src files since that is what end users use and that is
what we need to restrict. See
https://icseng.atlassian.net/browse/FRONTIER-2569

esx is a way to restrict from using specific new es features so that
users on older browsers do not get errors as much.

See
https://github.com/fs-webdev/eslint-config-frontier-react/pull/62/files
for the eslint-config-frontier-react pr.

Author: FSVetaz

demo/test/snapshots/linting-config.test.js.md

@@ -12,7 +12,7 @@ Generated by [AVA](https://ava.li).
       "env": {␊
         "cypress/globals": true,␊
         "jest/globals": true,␊
-        "es2021": true,␊
+        "es2022": true,␊
         "es6": true,␊
         "node": true,␊
         "browser": true␊
@@ -4121,7 +4121,7 @@ Generated by [AVA](https://ava.li).
       "env": {␊
         "cypress/globals": true,␊
         "jest/globals": true,␊
-        "es2021": true,␊
+        "es2022": true,␊
         "es6": true,␊
         "node": true,␊
         "browser": true␊

demo/test/snapshots/linting-config.test.js.snap

@@ -1,3 +1,4 @@
 module.exports = {
   extends: ['@fs/eslint-config-frontier-react/react', './es6', './qa'],
+  overrides: [{ files: ['src/**'], extends: ['@fs/eslint-config-frontier-react/esx'] }],
 }