Mediation analysis example

[antagomir]

Mention in some suitable chapter that also mediation analysis is supported by mia.

Or: exemplify the new mediation functionality in mia with a more detailed example. Avoid duplicating what is already in mia documentation and examples. But if OMA is a good place to explain more about the new method, then perhaps. Consider future maintenance burden for all new content.

Perhaps we should have a new Chapter on "Other methods" or "Advanced techniques", with miscellaneous content that does not make their own dedicated chapter yet?