Fix: Require ext-ctype

[localheinz]

This pull request

• explicitly requires the implicitly required ext-ctype

Spotted in sebastianbergmann/phpunit#4759.

💁‍♂️ Running

$ git grep ctype_

yields (among others)

src/Psalm/Internal/Codebase/ConstantTypeResolver.php:9:use function ctype_digit;
src/Psalm/Internal/Codebase/ConstantTypeResolver.php:202:                    } elseif (ctype_digit($key_type->value)) {

❗ You might be interested in taking a look at shivammathur/setup-php#487, where @shivammathur has already put capabilities in place that allow disabling all PHP extensions, and enabling those that are required. This allows detecting hidden dependencies on PHP extensions.

[weirdan]

Thanks!

[localheinz]

Thank you, @weirdan!

[drupol]

There's also this tool which can be useful: https://github.com/maglnet/ComposerRequireChecker