Cover Covid-19 network analysis

[briatte]

As suggested in #102 -- the Covid-19 pandemic must have generated its own slew of handbooks, guides, courses etc. on how to apply network analysis to epidemics, and to that one in particular.

If anyone who reads this happens to work in that field and has a few resources (of the same type as those already listed in the document: courses, handbooks and so on) to recommend, that would be much appreciated!