devel/py-jupyter-ydoc: Add py-jupyter-ydoc 0.2.3

jupyter_ydoc provides Ypy-based data structures for various documents used in
the Jupyter ecosystem. Built-in documents include:
- YBlob: a generic immutable binary document.
- YUnicode: a generic UTF8-encoded text document (YFile is an alias to
  YUnicode).
- YNotebook: a Jupyter notebook document.