Add mention of decoding optimizations in the what's new document.
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
index ac01236..6fb60af 100644
--- a/Doc/whatsnew/3.3.rst
+++ b/Doc/whatsnew/3.3.rst
@@ -1260,6 +1260,10 @@
* repeating a single ASCII letter and getting a substring of a ASCII strings
is 4 times faster
+* UTF-8 and UTF-16 decoding is now 2x to 4x faster.
+
+ (contributed by Serhiy Storchaka, :issue:`14624` and :issue:`14738`.)
+
Build and C API Changes
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