add a help page
from @andrii.neronov
I think I have a descent help page now for Fermi/LAT, written in the Help.md file at Renkulab:
https://renkulab.io/gitlab/astronomy/mmoda/fermi/-/edit/master/Help.md
Can be a good test to see if it can be made visible from the frontend on https://staging.odahub.fr/mmoda/ and, ideally, appear as a sub-section of more general MMODA manual of https://www.astro.unige.ch/mmoda/ .....
https://github.com/oda-hub/mmoda-frontend-module/issues/201a