[FEATURE] Configurable landing page / admin page

[tjcork]

Describe the feature you'd like and why

Instead of the landing page being hardcoded onto the base domain, it should be configurable onto any (sub)domain via .env. This is so that the base domain can be reserved for the web app / service that the launchkit is likely to support.

Placing the landing page on e.g. admin.yourdomain.com or portal.yourdomain.com will allow it to evolve into an admin portal, later even allowing all the update script wizards etc to run through it.

[freddy-schuetz]

Hi @tjcork , thanks for the cool idea.
However, that's not my focus right now, but I'll gladly take the idea on board for a later date.
If you want to do it yourself and make it available as a pull request, I'll be happy to include it!

Best regards,
Friedemann