Setting checkbox to checked in Form App
I have added the Mailchimp app to my contact form to give users the option to join mailinglist. I have this working well but the problem I have is setting the checkbox to checked on page load. I can't see what I am doing wrong, I saw on perch_content there is default field but it wasn't mentioned in the form docs.
I have this for the input field, form example
<perch:input type="checkbox" id="confirm" label="mailinglist" checked="checked" value="1" mailer="confirm_subscribe" />