I looked into this and it wasn't really easy to do. So I updated the jquery.h5validate.js file to make it possible.
Replace your version of the file with the one I have attached.
Then you can add a new attribute to your input field that you want to add the validation to like this:
<input type="email" validate="notspam"
And then add a function to defile what notspam means like:
<script>
function notspam(el,val) {
var notAllowed = /\.ru\s*$/i;
if (notAllowed.test(val)) return false;
return true;
}
</script>