[clang-tools-extra] [clang-doc] Add another test project to clang-doc (PR #97518)

[Paul Kirth via cfe-commits]

https://github.com/ilovepi requested changes to this pull request.

I'm a bit confused by the "advanced project", as it largely seems to be minor extensions to the `basic project`. I would expect that an "advanced project" would use a complicated structure and be much larger.  IMO if you're only adding some more language features, then they should be added to the existing `basic_project` already in tree.

https://github.com/llvm/llvm-project/pull/97518