Voting feature

When a product is "coming soon", a voting form is added under the label, allowing visitors to vote for the products they want the most.

The admins can then see in the dashboard which products are most wanted and prioritize the development of new products. A count of the votes is also available on each product page, right under the "Coming soon" checkbox.
I didn't use Ajax just because it was faster that way. Don't you think the `edd_coming_soon_voting_progress()` jQuery function makes the voting in progress clear enough?