Add a pre-commit hook to validate the Jupyter notebooks

[jhlegarreta]

At times, we manually edit the raw Jupyter notebooks (like https://github.com/carpentries-incubator/SDC-BIDS-dMRI/pull/137#discussion_r613573684) 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.