add more tutorials

[LegrandNico]

The following tutorials need to be expanded and rewritten:

• Multilevel embedding of Hierarchical Gaussian Filters
• Parameters recovery, prior predictive and posterior predictive sampling
• The cardiac filtering HGF could include an example of seasonality decomposition through value coupling

We need new tutorials on the following topics:

• Binary HGF with finite precision
• The multivariate normal HGF (once add input node that filter any parameters from the exponential distribution family #144 completed)