rwmb_frontend_validate and update $_POST value

Hello Nick,

Yes, you can update the $_POST value when validating the form. For example:

add_filter( 'rwmb_frontend_validate', function( $validate, $config ) {
	$_POST['field_id'] = 'test field value';
	rwmb_request()->set_post_data( $_POST );

    return $validate;
}, 10, 2 );

Following the documentation https://docs.metabox.io/actions/rwmb-before-save-post/