It is now possible to customize the emails sent to your users to confirm their email address ect.
Just run npx create-keycloak-email-directory, it will create a keycloak_email directory at the root of your project.
This directory should be tracked by Git (yarn add -A) You can start hacking the default template.
When npx build-keycloak-theme (yarn keycloak) is run, if the directory keycloak_email exists at the root of your project, it will be bundled into your .jar file and you will be able to select it in the Keycloak administration pages.