Describe the workflow you want to enable

Decision trees should have similar / identical options for all export formats.

Describe your proposed solution

Include the class_names argument.

Describe alternatives you've considered, if relevant

Overhauling the whole tree plotting and export system, to make very nice output easy to achieve. Right now each format is dependent on force layouts, matplotlib engines, and varies a lot.

Additional context

https://scikit-learn.org/stable/auto_examples/tree/plot_iris_dtc.html <- shows a very nice graph.
https://stackoverflow.com/questions/25274673/is-it-possible-to-print-the-decision-tree-in-scikit-learn <- printing the decision tree layout