Consider adding all possible native type hints for all PHP codes

[peter279k]

As title, since the php-7.2 version is minimum version at least, I think it's nice to all methods (including tests and src folders) have the native type hints (e.g. void and other new type hints).

[arcostasi]

Hello @peter279k, I believe it was added, in PHPStan is 100% with --level=max

[peter279k]

Hi @arcostasi, thanks for your reply.

I think I will make related PR at my available time and you may know what I talk about.