[clang-tools-extra] [clang-doc] Add standalone Markdown parsing library (PR #202991)

[Neil Nair via cfe-commits]

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@@ -0,0 +1,274 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Standalone Markdown parsing library for the LLVM ecosystem.
+///
+/// The parser takes plain paragraph text and returns a polymorphic tree of
+/// MDNode-derived objects allocated in a caller-supplied BumpPtrAllocator.
+/// Node types form a closed class hierarchy rooted at MDNode. Each concrete
+/// type carries exactly the fields it needs -- no overloaded Content field,
+/// no unused arrays. Use llvm::isa<>/cast<>/dyn_cast<> for type-safe
+/// downcasting; each concrete type provides classof() for this purpose.
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Neil-N4 wrote:

Rewrote

https://github.com/llvm/llvm-project/pull/202991