range can return strings

```php
function takesString(string $s) {}

takesString(range('A', 'Z')[0]);
```

> Parameter #1 $s of function takesString expects string, float|int given.

https://phpstan.org/r/89dbe414-2543-4c1d-a6b9-ba12f11566db

This should probably be implemented using a dynamic return type extension.