[clang] [clang] Implement CTAD for type alias template. (PR #77890)

[Erich Keane via cfe-commits]

================
@@ -96,6 +96,10 @@ C++20 Feature Support
   behavior can use the flag '-Xclang -fno-skip-odr-check-in-gmf'.
   (`#79240 <https://github.com/llvm/llvm-project/issues/79240>`_).
 
+- Initial support for class template argument deduciton (CTAD) for type alias
----------------
erichkeane wrote:

```suggestion
- Initial support for class template argument deduction (CTAD) for type alias
```

https://github.com/llvm/llvm-project/pull/77890