Add pre-commit hooks for jupyter notebooks

[jonbarker68]

Notebooks have problems in revision control as they contain a lot of non-content data, i.e. outputs and metadata that change each time the notebook is run. This can be fixed using pre-commit hooks.

• Can use nb-ensure-clean https://gitlab.com/iamlikeme/nbhooks to remove output cells plus metadata such as execution counts and times
• Can also add notebook pre-commit hooks for black and flake8 via https://github.com/nbQA-dev/nbQA.