build() {
    const { value = '', ...attrs } = this.config
    //Textareas do not have an attribute 'type'
    delete attrs['type']
    this.field = this.markup('textarea', this.parsedHtml(value), attrs)
    // Make the editor read only if disabled is set on the textarea
    if (attrs.disabled) {
      this.editorOptions.readonly = true
    }
    return this.field
  }
build a textarea DOM element, to be later replaced by the TinyMCE editor
@return {Object} DOM Element to be injected into the form.