[clang-tools-extra] [clang-doc] Add a border box to comments in HTML (PR #174541)

[Erick Velez via cfe-commits]

evelez7 wrote:

Thanks, I think I fixed it and I updated the preview. I had to clear my browser cache to see the new changes. I never noticed that there was dark theme support.

https://github.com/llvm/llvm-project/pull/174541