All changes to the documentation should go against the master branch.
The repository for the frontent is hosted @ https://github.com/hacs/frontend

First spin up the devcontainer

When you have that running issue the following comands:

yarn start

When this is running it spins up a dev server, which you can attach to from a Home Assistant instance that is running HACS.

To attach the development frontend add this to your Home Assistant installation that is running HACS:

panel_custom:

- name: hacs-dev-frontend

sidebar_title: HACS (Dev frontend server)

sidebar_icon: mdi:alert-circle

url_path: hacs_dev

js_url: http://localhost:5000/main.js

Change localhost for the IP of your devserver if not the same.