Rust: Add change note

rust/ql/lib/change-notes/2025-09-19-parameter-mad.md

@@ -0,0 +1,7 @@
+---
+category: feature
+---
+* The models-as-data format for sources now supports access paths of the form
+  `Argument[i].Parameter[j]`. This denotes that the source passes tainted data to
+  the `j`th parameter of it's `i`th argument (which must be a function or a
+  closure).