I need to do it without javascript.
For example, the form HTML rendered on the page normally looks like this:
<form action="/contact-us/#wpcf7-f713-p61-o1" method="post" class="wpcf7-form submitting" novalidate="novalidate" data-status="submitting">
But I need to add the custom attribue data-netlify="true"
so the form should end up like this:
<form action="/contact-us/#wpcf7-f713-p61-o1" method="post" class="wpcf7-form submitting" novalidate="novalidate" data-status="submitting" data-netlify="true">
There is a similar question over here. But that is for putting a custom attribute on the input, I need the custom attribute on the form itself.