doc: add "Known issues" to the 1.13 change log entry

ChangeLog

@@ -27,6 +27,12 @@ Fri Apr 21 2023 Łukasz Stolarczuk <lukasz.stolarczuk@intel.com>
 	- several fixes to support ppc64le architecture
 	- several fixes for issues found by Coverity tool
 
+	Known issues:
+	- The latest validation cycle exposed previously unknown persistency issues
+	related to pmem2 async functions (DEPRECATED) and miniasync (EXPERIMENTAL):
+	#5596 and #5597. Both will be removed in the PMDK 1.14 release. These issues
+	do NOT affect any other PMDK library.
+
 Tue Aug 25 2022 Łukasz Plewa <lukasz.plewa@intel.com>
 
 	* Version 1.12.1