Publish a public roadmap

[mlorenzoitx]

Motivation

I don't see a public roadmap for gh-sherpa, isn't bad but having a public roadmap is useful to know what we can expect in new release, when a new release will be published and what features are being developed.

Here you have a roadmap examples:
[PROXMOX] (https://pve.proxmox.com/wiki/Roadmap#Proxmox_VE_8.1)
[Opnsense] (https://opnsense.org/about/road-map/)

you can publish a simple markdown file like roadmap.md

Acceptance criteria

• A roadmap is published