Add new section `Tutorials` in readme/index.md

with a link to the tutorial section of jso.dev (and precising that we can select the right tag).

Open readme/index.md and review how existing sections and links are formatted. Add a Tutorials section linking to the tutorial section of jso.dev and explain that readers can select the appropriate tag. Done means the section and link are present and the wording clearly describes tag selection.

Written by the indexing model from the issue text.