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* add complete tutorial notebooks since their execution is deactivated on the docs server
* exclude some notebooks from automatic documentation build because they take very long
* update documentation with how tos and gallery
* add matplotlib to docs requirements
* added sphinx gallery to docs requirements
* blacken whole package
* add documentation autosummaries for layers and activations. Small docstring modifications
* first version of Sinabs gallery instead of tutorial notebook that plots neuron models
* added pre-commit hooks for black