Added change notes.

Author: Sebastian Bauersfeld

java/ql/lib/change-notes/2022-08-19-string-taint-models.md

@@ -0,0 +1,5 @@
+---
+category: minorAnalysis
+---
+* Added taint flow models for the `java.lang.String.(charAt|getBytes)` methods.
+* Improved taint flow models for the `java.lang.String.(replace|replaceFirst|replaceAll)` methods. Additional results may be found where users do not properly sanitize their inputs.