Add: Update docs with the new changes.

Update ReleaseNotes.rst with the changes made

Author: da-viper

clang-tools-extra/docs/ReleaseNotes.rst

@@ -285,6 +285,10 @@ Changes in existing checks
   <clang-tidy/checks/modernize/use-using>` check to fix function pointer and
   forward declared ``typedef`` correctly.
 
+- Improved :doc:`modernize-use-using
+  <clang-tidy/checks/modernize/use-using>` by ignoring ``typedef`` declaration in
+  ``extern "C"`` scope.
+
 - Improved :doc:`performance-faster-string-find
   <clang-tidy/checks/performance/faster-string-find>` check to properly escape
   single quotes.
@@ -325,6 +329,7 @@ Changes in existing checks
   identify calls to static member functions with out-of-class inline definitions.
 
 
+
 Removed checks
 ^^^^^^^^^^^^^^
 

clang-tools-extra/docs/clang-tidy/checks/modernize/use-using.rst

@@ -28,6 +28,15 @@ After:
   using R_t = struct { int a; };
   using R_p = R_t*;
 
+The checker ignores `typedef` within `extern "C" { ... }` blocks.
+
+.. code-block:: c++
+
+  extern "C" {
+
+    typedef int InExternC; // Left intact.
+  }
+
 This check requires using C++11 or higher to run.
 
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