Release 0.5.0

• allow suitably authorized users to create notebooks on behalf of others
• add optional token-based authentication
  for accessing iodide's API endpoints without a github or openidc session.
• Pyodide has been upgraded to version 0.10.0. This includes the new packages:
  html5lib, pygments, beautifulsoup4, soupseive, docutils, bleach
• disable automatic saving and interactivity if viewing an out of
  date copy of the notebook (#1593)
• use maintained markdown-it-katex package
• automatically flush any pending notebook saves to the server if the
  user is navigating away from the iodide tab
• Fix an unlikely race condition where a notebook is found to be out
  of date inside the throttle interval of a server autosave