Is your feature request related to a problem? Please describe.

We should be able to override email template in the custom theme.

Describe the solution you'd like (*)

Add a new action similar to the Override this file in a project theme. This action should override email templates in custom themes. Read documentation before starting development: https://developer.adobe.com/commerce/frontend-core/guide/templates/email/.

Additional context

Mainline branch: 5.0.0-develop