Add Documentation generation and upload to github pages

[hatcat]

Documentation list

Public API

Implementation and maintenance

Tutorials

Geometry and Givens matrices

Dynamically expanding matrix (new row data at run time)

Integrating mdspan

Replacement algorithms

Units

[hatcat]

I guess most of this would go in the wiki.

[Twon]

The plan is to automatically generate documentation and upload it to the project's respective Github pages. We can use Doxygen to generate tags from the code, and then use Sphinx to generate the HTML from mdfiles controlling the structure of the document as we want it. This is the approach used by fmt and the mp-unit projects currently. Take a look at how this may look:

MPUnits:

• md files to control the document: https://github.com/mpusz/mp-units/tree/master/docs/users_guide
• Resulting documentation uploaded to the projects Github pages: https://mpusz.github.io/mp-units/latest/