Fix cookie in request for future chrome versions

[Metashaker]

This is still not an issue, bit will be in future Chrome verisons. I get the following warning after I succesfully suscribe users to my newsletter:
A cookie associated with a cross-site resource at https://list-manage.com/ was set without the SameSite attribute. A future release of Chrome will only deliver cookies with cross-site requests if they are set with SameSite=None and Secure.

[revolunet]

Well, this is from mailchimp so this cannot be fixed here unless they provide a real API to add subscribers

[Metashaker]

Okok, will bring it to their attention!