Update CHANGELOG

Author: mikkelfj

CHANGELOG.md

@@ -60,6 +60,7 @@
   disabled in build already, but this may help some users (#313).
 - Fix %d vs uint32 type in some printformatting (#315).
 - Fix UB in builder, memsetting 0 bytes of null pointer (#344).
+- Fix GCC 15 warning in grisu3 (#338).
 
 ## [0.6.1]