Using MultiDocumenter

[sethaxen]

Some of ArviZ's functionality is split out into smaller lightweight packages, and this will continue until ArviZ is more or less a super-package that just reexports all or some of the functionality of these component packages. Each component package has its own hosted documentation. A downside to this approach is that there's some redundancy in docs. e.g. we need to document usage of InferenceData here, but we should also document it in InferenceObjects.jl, so keeping those docs consistent adds maintenance burden.

https://github.com/JuliaComputing/MultiDocumenter.jl may solve this. If we already have some repos with docs builds stored in a branch on GitHub, MultiDocumenter will allow to build a docs site that contains the docs of the individual packages and has a unified search feature.