[clang-tools-extra] [clang-doc] Add Markdown AST node type definitions (PR #205609)

[Neil Nair via cfe-commits]

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@@ -6,5 +6,6 @@ set(LLVM_LINK_COMPONENTS
 
 add_clang_library(clangDocSupport STATIC
   File.cpp
+  Markdown.cpp
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Neil-N4 wrote:

will address the constructor in a standalone patch. also moved Markdown.cpp to its own clangDocMarkdown target

https://github.com/llvm/llvm-project/pull/205609