Documenting InferenceData usage

[sethaxen]

Now that #191 is merged, we should document some examples of how users can use InferenceData with DimensionalData for those who are not yet familiar with DimensionalData's API before making a release.

Python ArviZ already has such a tutorial for its xarray-backed implementation that could be a useful reference: https://python.arviz.org/en/latest/getting_started/WorkingWithInferenceData.html#working-with-inferencedata

Edit: it would be a good idea to also include examples of custom plotting with Plots or Makie using InferenceData, but this could be documented after this release

[sethaxen]

Implemented in #201