Make PHPStan run on CI

[matsuo]

This PR adds a CI job with phpstan (level 0) and I will resolve everything until it's green.

[till]

@matsuo I merged the other, so feel free to rebase this, e.g. if pear is the origin remote:

git fetch origin
git rebase origin/master

[matsuo]

Thanks for your kindness!
After adding “const ERROR_INVALID_PARAM_TYPE = 106;” to File/IMC.php, the detection result by PHPStan at level 0 is gone.