0.12.8

🚀 Features

Authenticated SpotNet dataset @elaubsch (#688)

This PR adds the SpotNet dataset to the list of new authenticated datasets, following the established pattern. It also adds a SpotNetExampleData class, which loads the example data for the Polaris example notebooks. This class deviates slightly from the existing pattern for loading data in order to accommodate for the different file types that need to be loaded. The SpotNet dataset has also been added to the datasets gallery in the documentation.