Add CAPTCHA option to WooCommerce Guest Checkout page

Hello,

I see in WP Security > Brute Force > CAPTCHA Settings that there are options to enable a CAPTCHA on the login, lost password, and registration form pages of WooCommerce. However, there isn’t an option to enable it on the guest checkout page, which would be great to have.

We noticed someone (or some bot) trying to repeatedly create orders through our WooCommerce site using a fraudulent credit card, and it was blowing up our emails and bombarding our order list, so having this feature would help reduce that considerably.