Add instructions on how to use Sphinx to example workflow

[peanutfun]

Is your feature request related to a problem? Please describe. The Example Workflow page in the docs demonstrates very verbosely how different comment blocks are transformed into RST. However, the workflow falls short of showing how to get an actual documentation from the RST. I realize that this can all be looked up in the Sphinx documentation but I think it would be helpful for users that do not have a RST toctree already. Since CMake is mostly used for C/C++ and Sphinx is typically used to document Python code, chances are high that users don't have a working Sphinx setup in their build.

Describe the solution you'd like Extend the example workflow with instructions for creating a Sphinx build. I did it the following way:

• Install Sphinx.
• Create a sub-directory in the project build directory.
• Enter this directory and call sphinx-quickstart. Follow the instructions.
• Run cminx on the project and set the sub-directory as output directory.
• Create an index RST file with a toctree (This is not technically needed, but otherwise you just get a module index).
• Run sphinx-build in that directory.

Since the "translation" from CMake comments to RST is demonstrated a lot in other parts of the docs, the example could also be shortened to improve the readability of the doc page.

Describe alternatives you've considered None.

Additional context None.

[ryanmrichard]

I think this is a great idea. I'll go ahead and work on it now.

[ryanmrichard]

@peanutfun sorry should have pinged you regarding #114. When you get a chance take a look at #114 and let me know if that addresses your concerns and/or if there's more that should be added.