[clang-tools-extra] [clang-doc] add nested namespace test case (PR #97681)

[Paul Kirth via cfe-commits]

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@@ -0,0 +1,340 @@
+// RUN: clang-doc --format=html --output=%t/docs --executor=standalone %s
+// RUN: clang-doc --format=md --output=%t/docs --executor=standalone %s
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ilovepi wrote:

Why no `mkdir`? I presume because clang-doc will make it, but the test shouldn't rely on that behavior. Plus we want to be sure each run is isolated, so starting w/ `rm -rf %t && mkdir %t` is a good practice if you need a directory. also, probably don't need `docs`...

https://github.com/llvm/llvm-project/pull/97681