Jupyter-book: Add support to display conda environments and provide environment.yml

[mmcky]

It would be nice to be able to have a page environment.html that publishes the conda versions used to compile a website / book. Perhaps we can write a simple sphinx extension to do this work.

.. conda-environment:: <environment.yml>
   :show-versions:

and myst

```{conda-environment} <environment.yml> :show-versions: ```

This would enable a user to download a support environment.yml file and would build a support page with details of versions of software used with :show-versions option.

[choldgraf]

I really like this idea! We should do the same for requirements.txt if provided

[choldgraf]

This would be a nice addition as a separate sphinx package - maybe sphinx-dependencies?

[jmason86]

I found this issue when looking to see if it's possible to include the environment.yml as a download for readers right alongside the .ipynb and .pdf under the download mouseover button at the top of notebook pages. Would that be a part of this issue too or should I open a new one with this enhancement request? Or is this possible already?

[choldgraf]

interesting - I think it could be its own issue as it'd probably be more tightly-scoped than this one.

[jmason86]

On it.