code: function getFormData(){
      var form = this.form;
      var selector = ['input', 'select', 'textarea'].join(',');
  
      return [].slice.call(form.querySelectorAll(selector))
        .filter(Mailto.formDataFilter)
        .map(Mailto.formDataMapper(form));
    }
docs: Returns the filtered values of a form.
  
  They are basically:
  - for named options
  - one entry per input/checked/selected option (even if they have the same name)
  
  @api
  @returns {Array.<{name: String, label: String, value: String|Boolean|Number}>}