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

[Nico Weber via cfe-commits]

nico wrote:

Looks Like this might break tests: http://45.33.8.238/linux/141118/step_7.txt

Please take a look and revert for now if it takes a while to fix.

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