Make eslint check ECMAscript 2022

This allows using public and private class fields, which are supported in all major browsers since years, (but just made
it into ECMAScript 2022).
See
<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Public_class_fields#browser_compatibility>
and <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Private_elements#browser_compatibility>.

.eslintrc.js

@@ -8,7 +8,7 @@ module.exports = {
         'plugin:unicorn/recommended',
     ],
     parserOptions: {
-        ecmaVersion: '2020',
+        ecmaVersion: '2022',
         sourceType: 'module',
     },
     ignorePatterns: [