`is_non_empty_string('0')` returns `false`

[AlwinGarside]

The is_non_empty_string() function currently follows PHP's default non-strict comparison logic. This means the string '0' evaluates as "empty".

This is not the intended behavior of is_non_empty_string(). It is intended to function as a type guard for PHPStan's non-empty-string type, which doesn't consider the string '0' to be empty.

The functions should be updated accordingly:

function is_non_empty_string(mixed $value): bool
{
    return is_string($value) && $value !== '';
}

[AlwinGarside]

Fixed in #26