[clang-tools-extra] [clang-doc] add enum test (PR #97679)

[Paul Kirth via cfe-commits]

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

LGTM, modulo some nits. I do think you may want to have a separate prefix for the lines, but if you change `--check-prefix=` to `--check-prefixes=HTML-ANIMAL,HTML-ANIMAL-LINE`, you should be able to check them w/o having to rewrite everything. Plus keeping the LINE comments right after the source line makes it a lot easier to keep the tests stable.

https://github.com/llvm/llvm-project/pull/97679