Add changelog

Author: thiggy1342

ruby/ql/lib/change-notes/released/0.3.1.md

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+## 0.3.1
+
+### Minor Analysis Improvements
+
+- Calls to `ActiveRecord::Relation#annotate` have now been added to `ActiveRecordModelClass#sqlFragmentArgument` so that it can be used as a sink for queries like rb/sql-injection.