Add custom font on WordPress Woocommerce plugin

**PLEASE READ THE DESCRIPTION**

I'm using this plugin for personalize WordPress and Woocommerce emails design

Reference link:
https://emailcustomizer.com/
or
https://codecanyon.net/item/email-customizer-for-woocommerce-with-drag-drop-builder-woo-email-editor/22400984

I would like to add a custom font because basically there are only 12 fonts.
I'm not sure if is possible to do that so you need to check by the demo the solution for add a font in this plugin in any part of it:

https://emailcustomizer.com/demo/woo/wp-login.php

I would like to have "Montserrat" font.

Thanks