C++: Add change note.

Author: MathiasVP

cpp/ql/lib/change-notes/2023-03-16-use-use-flow.md

@@ -0,0 +1,8 @@
+---
+category: majorAnalysis
+---
+* A new C/C++ dataflow library (`semmle.code.cpp.dataflow.new.DataFlow`) has been added.
+  The new library behaves much more like the dataflow library of other CodeQL supported
+  languages by following use-use dataflow paths instead of def-use dataflow paths.
+  The new library also better supports dataflow through indirections, and new predicates
+  such as `Node::asIndirectExpr` have been added to facilitate working with indirections.