[DRAFT] Upgrade to JupyterBook

[jnywong]

Closes #207, https://github.com/2i2c-org/meta/issues/941

[jnywong]

toctree directives from Sphinx external-toc gives the warning

/home/jovyan/docs/about/service/index.md:22: WARNING: toctree directive not expected with external-toc [etoc.toctree]
/home/jovyan/docs/about/service/index.md:45: WARNING: toctree directive not expected with external-toc [etoc.toctree]
/home/jovyan/docs/about/service/index.md:67: WARNING: toctree directive not expected with external-toc [etoc.toctree]

tableofcontents and contents directives from Jupyter Book docs are not sufficient since they refer to toctrees defined within the same page rather than cross-referencing to different pages.

[jnywong]

toctree directives from Sphinx external-toc gives the warning

/home/jovyan/docs/about/service/index.md:22: WARNING: toctree directive not expected with external-toc [etoc.toctree]
/home/jovyan/docs/about/service/index.md:45: WARNING: toctree directive not expected with external-toc [etoc.toctree]
/home/jovyan/docs/about/service/index.md:67: WARNING: toctree directive not expected with external-toc [etoc.toctree]

tableofcontents and contents directives from Jupyter Book docs are not sufficient since they refer to toctrees defined within the same page rather than cross-referencing to different pages.

@agoose77 has reassured me that the toctree directive is safe to use in Jupyter Book for now if we are explicit about read-only cases.

[jnywong]

Running the Jupyter Book linkechecker gives

$ jb build . -q --builder linkcheck
Running Jupyter-Book v1.0.0
Source Folder: /home/jovyan/docs
Config Path: /home/jovyan/docs/_config.yml
Output Path: /home/jovyan/docs/_build/html
/home/jovyan/docs/about/distributions/index.md:19: WARNING: broken link: https://docs.2i2c.org/en/latest/admin/howto/content.html (404 Client Error: Not Found for url: https://docs.2i2c.org/admin/howto/content.html)
/home/jovyan/docs/about/distributions/index.md:19: WARNING: broken link: https://docs.2i2c.org/en/latest/admin/howto/data.html (404 Client Error: Not Found for url: https://docs.2i2c.org/admin/howto/data.html)
/home/jovyan/docs/admin/howto/control-user-server.md:29: WARNING: broken link: https://github.com/jupyterlab/rtc (404 Client Error: Not Found for url: https://github.com/jupyterlab/rtc)
/home/jovyan/docs/admin/howto/manage-users.md:147: WARNING: broken link: https://infrastructure.2i2c.org/en/latest/howto/configure/auth-management.html#switch-identity-providers-or-user-accounts (404 Client Error: Not Found for url: https://infrastructure.2i2c.org/howto/configure/auth-management.html)
/home/jovyan/docs/topic/cloud-costs.md:65: WARNING: broken link: https://nbviewer.jupyter.org/github/berkeley-dsep-infra/datahub-usage-analysis/blob/master/notebooks/03-visualize-cost-and-usage.ipynb (404 Client Error: Not Found for url: https://nbviewer.org/github/berkeley-dsep-infra/datahub-usage-analysis/blob/master/notebooks/03-visualize-cost-and-usage.ipynb)
/home/jovyan/docs/about/service/comparison.md:476: WARNING: broken link: https://noteable.io/ (HTTPSConnectionPool(host='noteable.io', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self-signed certificate in certificate chain (_ssl.c:1007)'))))
(topic/cloud-costs: line   65) broken    https://nbviewer.jupyter.org/github/berkeley-dsep-infra/datahub-usage-analysis/blob/master/notebooks/03-visualize-cost-and-usage.ipynb - 404 Client Error: Not Found for url: https://nbviewer.org/github/berkeley-dsep-infra/datahub-usage-analysis/blob/master/notebooks/03-visualize-cost-and-usage.ipynb
(about/service/comparison: line  476) broken    https://engagelively.com/ - HTTPSConnectionPool(host='engagelively.com', port=443): Max retries exceeded with url: / (Caused by ConnectTimeoutError(<urllib3.connection.HTTPSConnection object at 0x7fd4c41fe6b0>, 'Connection to engagelively.com timed out. (connect timeout=None)'))
rediraffe: Redirect generation skipped for linkcheck builders.
build finished with problems.

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Building your book, returns a non-zero exit code (1). Look above for the cause.

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