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

[Paul Kirth via cfe-commits]

ilovepi wrote:

A few meta comments on the particulars of the commit title and message:
1. Please change the title to only have the [clang-doc] tag. This doesn't impact `clang` at all. We use the`[tag] Title` convention to make it easy to understand where the changes are, and what they affect. Here something appropriate is either `[clang-doc] Add basic e2e test` or `[clang-doc][test] Add basic e2e test`.
2. The first comment on GitHub is special in a PR, as its the commit body. Ideally, it would have a description of what your change is doing and why. For tests, its often beneficial to put some rationale or explanation in the commit message, if there isn't a place to document it in the source.
3. If you only reference an issue, it just creates a cross ref. If your commit should fix or close the issue, there are special keywords you can put in the commit body for that (see [this reference](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword)).

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