[jupyter-book] Support for numbered references

[mmcky]

We now have a test set for configuring numbered references using sphinx numref

https://mmcky.github.io/ebp-test-projectstructure/parts_chapter.html#numref-numbered-references-html-and-latex

The test set html shows it can be used in the part_chapter structure of jupyter-book however we will need to fix part numbering. It will also work for latex

• [ ] fix part numbering due to multiple toctree elements. This is being worked on here

this will work for html and latex but will need to get sphinx numbering fixed.

[mmcky]

This issue should be transferred to

https://github.com/executablebooks/sphinx-jupyterbook-latex