Implement ExpressionLanguage Parser

[Haehnchen]

$language = new ExpressionLanguage();
$language->register('lowercase', function ($str) {
    return sprintf('(is_string(%1$s) ? strtolower(%1$s) : %1$s)', $str);
}, function ($arguments, $str) {
    if (!is_string($str)) {
        return $str;
    }

    return strtolower($str);
});

https://github.com/symfony/symfony-docs/blob/086885b98eb9b36eea465384fe204485b1bca463/components/expression_language/extending.rst#id1
symfony/symfony-docs#4289

[stepanets]

Would be great to add at least brackets parsing

[tigokr]

it would be a good feature