[clang-tools-extra] [clang-doc] Add --asset option to clang-doc (PR #94717)

[Paul Kirth via cfe-commits]

https://github.com/ilovepi approved this pull request.

Modulo a few small nits, this is LGTM. Once those are addressed and CI passes, I can land this for you.

https://github.com/llvm/llvm-project/pull/94717