Document development setup

[Ana Gelez]

Especially how to setup HTTPS (I think Caddy and mkcert is the way to go (we need mkcert since caddy uses self signed certificates for local sites, which are rejected when federating))

[Mina Galić]

I've been using mod_md and it as quite easy too! compared to the usual ceremony…

[Ana Gelez]

I added explanations about Caddy, but if you want to document what you are doing with mod_md, @igalic feel free to do so!