Add a pre-commit hook to validate the Jupyter notebooks

[jhlegarreta]

At times, we manually edit the raw Jupyter notebooks (like #137 (comment)) and break the notebooks and they effectively become unusable.

Although the CI tests in place would potentially detect such cases, this is not ideal; we would like the CI tests to spend time in executing the cells, rather than exiting because the file cannot be parsed.

Adding a pre-commit hook that is able to ensure that the files can at least be parsed could be a solution for this.