Support Jupyter notebooks / .ipynb files

Provide some scaffolded support for uploading .ipynb Jupyter notebooks and displaying them. Current options for presenting Jupyter notebooks are all based on linking to some nbconvert-based output. nbconvert does have a --to markdown option, but GitHub pages wouldn't run nbconvert on push. So this would likely be a script / notebook that would be run by a user when adding an .ipynb file to the repository, which calls nbconvert to generate the markdown file in the appropriate folder, then adding appropriate YAML metadata.

This would also need a defined way to for users to point to where .ipynb files are located and specify metadata.