How to customize Allure Report's HTML without change allure2's code base

[lance-cheng-asus]

Hi there,
In my use case, I'd like to add custom Microsoft Clarity, Google Analytics.
I found the html template here

allure2/allure-generator/src/main/resources/tpl/index.html.ftl

Line 30 in 7402869

<script async src="https://www.googletagmanager.com/gtag/js?id=G-FVWC4GKEYS"></script>

however, modifying this template requiring additional study (fork a allure2 branch, modify the template, learn how to build a allure2 package...). Is there a way to add custom HTML without change allure2's source code?

Are there any docs for beginner about how to develop and build allure2?