New Doxybook/Jekyll-based GitHub Pages documentation infrastructure (take two)

[brycelelbach]

This PR (a revived version of #1475) introduces a new documentation infrastructure. It generates Doxygen XML output, and then uses the Doxybook2 framework to generate GitHub Flavored Markdown. That GitHub Flavored Markdown is rendered using the Jekyll just-the-docs theme.

The final product is documentation in the style of the C++ Standard and cppreference that can be deployed to GitHub Pages. For each class or Doxygen group, there is a code synopsis of all entities, followed by a section that contains detailed descriptions of them. Users can browse the docs using the sidebar or with just-the-docs powerful builtin search mechanism.

There are two scripts that can be used to locally build and host the docs:

• docs/generate_markdown.bash: This runs Doxygen and then Doxybook to generate the Markdown for the API docs.
• docs/serve_jekyll_locally.bash: This will start a local Jekyll server that will host the docs. You need to run docs/generate_markdown.bash first. Jekyll will build the HTML site when it starts, which takes a few minutes.

To build locally, you need to install Doxygen, Ruby (Debian package: ruby-dev), and Bundler (Debian package: bundler), which you should be able to do through your system's package manager.

You'll also need to build Doxybook from source, which is pretty easy to do. You'll need vcpkg to install Doxybook's dependencies - note that you'll need to specify --head when installing the inja dependency to ensure you get the correct version:

vcpkg install argagg catch2 fmt dirent fmt nlohmann-json rang
vcpkg install --head inja

Note that the above command install inja may fail within the NVIDIA VPN due to GitHub API rate limits (see microsoft/vcpkg#19177). As an alternative, you can just grab and build inja, and then add the inja build directory to your CMAKE_PREFIX_PATH when building Doxybook.

Automated builds and deploy of the docs to GitHub pages are in place. The rendered docs from the tip of this branch can be seen at https://nvidia.github.io/thrust

[brycelelbach]

run tests

[alliepiper]

run tests

[brycelelbach]

run tests

[alliepiper]

DVS CL: 30976967

[brycelelbach]

Thanks Allison.

[brycelelbach]

gpuCI and DVS are passing, I think we are good to merge.