How to make a new web component

[Fabien Bodard <gambas.fr@xxxxxxxxx>]

I begin to understand the basis but I stuck on adding this  (LeafLet map) :

<link rel="stylesheet" href="
https://unpkg.com/leaflet@1.9.4/dist/leaflet.css";
integrity="sha256-p4NxAoJBhIIN+hmNHrzRCf9tD/miZyoHS5obTRR9BMY="
crossorigin="" />

<script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js";
integrity="sha256-20nQCchB9co0qIjJZRGuk2/Z9VM+kNiyxNV1lvTlZBo="
crossorigin=""></script>

How I'm I supposed to do to add this pre requise. ?

(I've read a big part of the web.gui code but nothing about external js
code)

Thank you
-- 
Fabien Bodard