Variabiliy Atlas for ETCCDI climate extreme indices

For more information, see the sidebar (click '>' top left) or the accompanying publication TODO: add link onced published.

Note to reviewers:

This is a preliminary version of the atlas for review. Please feel free to include suggestions or comments on the atlas in your review. The final version will include more detailed information on background, data, and methods as well as references to the relevant locations in the final manusript. The source code is available on GitHub: https://github.com/lukasbrunner/etccdi_internal_variability