Check for static type hints and declare(strict_types=1);

[tmotyl]

It would be nice if the PHP_CodeSniffer actions are extended to check for static type hints and whether declare(strict_types=1); is missing.
e.g. using https://github.com/slevomat/coding-standard
https://github.com/slevomat/coding-standard#slevomatcodingstandardtypehintsdeclarestricttypes-

[fooman]

@tmotyl Thanks for your suggestion. This action is using the upstream Magento Coding Standard. I suggest following this issue here magento/magento-coding-standard#33 - once available it will be utilised by this github action as well.