[clang-tools-extra] [clang-doc] Add helpers for Template config (PR #138062)

[Paul Kirth via cfe-commits]

ilovepi wrote:

### Merge activity

* **May 22, 9:19 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/138062).


https://github.com/llvm/llvm-project/pull/138062