[docs] Guides page is blank

[ivrolan]

The page https://flax.readthedocs.io/en/latest/guides/index.html lands to an existing page but it is blank. This page is used as a reference in some other resources, like https://github.com/rcrowe-google/Learning-JAX slides.

Is this intended? I think it would be nice if it links to other Basic Guides and Advanced Guides pages.