JupyterBook integration tracking issue

[melissawm]

Currently, sphinx-tags correctly generates tags for a JupyterBook, but there are some issues:

• In individual tags pages, duplicate links may be generated to the pages containing that tag unless we use exclude_patterns : ["_build"] in the config.yml file for the book. Actually, this only happens if the jupyter-book build is run twice without deleting the _tags folder first.
• Because JupyterBook uses the external-toctree extension, the individual autogenerated toctrees for the tags pages raise a WARNING: toctree directive not expected with external-toc [etoc.toctree]. A workaround is to use

sphinx:
  config:
    suppress_warnings: ["etoc.toctree"]

in the JupyterBook config.yml file.

cc @mikofski