fix: avoid cloning accessor properties

[Hanake0]

Ignore accessor properties to prevent assigning a “value” field when a getter or setter exists

This is my first pr, so please tell me if i missed someting.

This pr prevents the error "TypeError: Invalid property. 'value' present on property with getter or setter." when trying to parse an object with a getter or setter.

As an example, you would need to pass process.env with an spread operator({ process.env }) so it could be validated and not throw an error by the lib. With this fix, now it can be validated correctly without the spread operator.

I think the test "can clone process.env" at clone.test.ts might need to be changed to reflect this new behavior.

[ssalbdivad]

Thanks for the PR! Need to think about the implications a bit and will take another look after 2.1.0