Updating the example data

Metadata for ArviZ’s example datasets (which are loadable by load_arviz_data) is stored in the arviz_example_data repository. This repo has been embedded into the arviz repo at /src/arviz_base/example_data using git subtree with the following command:

$ git subtree add --prefix src/arviz_base/example_data https://github.com/arviz-devs/arviz_example_data.git main --squash

When arviz_example_data is updated, the subtree within the arviz repo also needs to be updated with the following command:

$ git subtree pull --prefix src/arviz_base/example_data https://github.com/arviz-devs/arviz_example_data.git main --squash

Moreover, to keep the size of the wheel and sdist for arviz-base as small as possible, the code folder of arviz_example_data is also removed as it contains some jupyter notebooks and csv files.