README rewrite for stable release

Squashed commit of the following:

commit 90dc048
Author: João S. O. Bueno <[email protected]>
Date:   Sun Aug 11 14:51:24 2024 -0300

    Readme: rewrite roadmap

commit ed5429a
Author: João S. O. Bueno <[email protected]>
Date:   Sun Aug 11 14:34:17 2024 -0300

    README: describe the different backends

commit a47d8cd
Author: João S. O. Bueno <[email protected]>
Date:   Sun Aug 11 13:03:06 2024 -0300

    Further documenti g the project in the README

commit f0d498e
Author: João S. O. Bueno <[email protected]>
Date:   Sun Aug 11 12:10:05 2024 -0300

    Keep improving README