Add use cases to the documentation

[ismael-lajaaiti]

Use cases illustrating the following features should be added to the documentation:

• non-trophic interactions (e.g. reproduction of Miele 2019) First use cases. #107
• mortality term First use cases. #107
• temperature dependence (@hanamayall you can simply put the use cases that you'll use for the manuscript)
• explicit nutrient intake (@evadelmas)
• interaction with the extension package EcologicalNetworkStability.jl (e.g. reproduction of Dominguez-Garcia 2019)

[iago-lito]

@ismael-lajaaiti Can we tick a few boxes here now that #107 has landed? What's still needing to be done? :)

[ismael-lajaaiti]

There is still two boxes to tick, nutrients use case and document EcologicalNetworksStability. We need to wait for the 1st one but the 2nd one is actually a bit out-of-scope of this issue, so we can forget about it for now.
Also to be clear, use cases are not yet incorporated in the documentation but are stored in a folder within package.
Anyway, I think that as soon as Eva submits her use case (that last one that we are waiting for) we can close this PR and open two new ones : one to incorporate this use case within the online documentation and another one to create documentation page about the companion package EcologicalNetworksStability. Does it seem good to you?

[iago-lito]

Sure. Regarding the integration within the doc, I think it's already covered by #118.

[iago-lito]

Closing in favour of #118.