[clang-tools-extra] [clangd] [C++20] [Modules] Introduce initial support for C++20 Modules (PR #66462)

[kadir çetinkaya via cfe-commits]

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@@ -48,6 +48,9 @@ Major New Features
 Improvements to clangd
 ----------------------
 
+- Introduced exmperimental support for C++20 Modules. The experimental support can
+  be enabled by `-experimental-modules-support` option.
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kadircet wrote:

i think we should also document current limitations here (we can update them as we implement more).

https://github.com/llvm/llvm-project/pull/66462