Plugin C++ API documentation

[alxbilger]

I've been playing with modern documentation tools to document C++ code. I started with a small plugin: https://github.com/SofaDefrost/SofaCUDALinearSolver

Checkout the following pull request:
SofaDefrost/SofaCUDALinearSolver#2

It allows to:

• Generate the doc when there is a commit in the main branch
• Publish it in the branch: gh-pages

The repository is configured with GitHub pages, built from the gh-pages branch. The result is at: https://sofadefrost.github.io/SofaCUDALinearSolver/. Thanks to the GitHub action, the documentation website will always be up-to-date with the main branch.

Note that a documentation website is a bit overkill for this plugin, but it is a good start for a bigger plugin.

[hugtalbot]

Wow, nice!! Thanks for sharing @alxbilger