[clang-tools-extra] [llvm] [clang][clang-doc] Add basic e2e test to clang-doc (PR #93928)

[Paul Kirth via cfe-commits]

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

Screen shots don't belong in the commit message. Public URLs are often OK for reference to LLVM source or a standards doc, but do make sure those are permalinks, and not pointed to somein on say the `main` brnach, which will change over time. 

In general, prefer including text and format it using markdown. This will show up in terminals and the GitHub UI equally well.

https://github.com/llvm/llvm-project/pull/93928