add a page to the documentation explaining
- FONLL plays on both grids and ekos, so it can not only be dealt here
- point to https://pineko.readthedocs.io/en/latest/theory/fonll.html for a detailed explanation
- say this is only available for DIS at the moment, but as explained in [cite nFONLL paper] it can be generalized to all generators
add a page to the documentation explaining