[SKIP-CI] Started releases notes for release 3.1-13

ReleaseNotes.md

+# v3.1-13
+
+## Summary
+
+### Features
+
+### Bug fixes
+
+- cta/CTA#941 Slow `cta-admin sq` even when there is very little activity
+
 # v3.1-12
 
 ### Features