This module allows you to add additional HTML attributes for any field.
If your site is managed via Composer, use Composer to download the module.
composer require drupal/field_attribute:^1.0
Or
Install the module as any other module.
Enable the module in 'Extend' page (/admin/modules).
Or
use Drush: drush en field_attribute
The field formatter attributes settings are found in the Manage display tab for content types, users, and other entities. A options element is available for each textfield field formatter, revealed by using the formatter settings edit button (Gear wheel icon) for that field.