Provide complete workflow

[psychemedia]

Ideally create a full set of tools for:

• generating Sphinx XML from markdown or Jupyter notebook
• generating OU-XML from Sphinx XML
• validating OU-XML

Nice to haves:

• spellchecking on markdown
• formatting and linting of code

[psychemedia]

Generating Sphinx XML:

In SOURCE_DIR, something like:

#conf.py
extensions = ['myst_parser']
source_suffix = ['.ipynb', '.md']

pip install myst-nb
mystnb-docutils-xml path/to/notebook.ipynb output.xml

We need to update the sphinxXml2ouXml builder to accept a path.