Add change note

Author: hvitved

shared/dataflow/change-notes/2024-05-06-param-return-nodes.md

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+category: minorAnalysis
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+* The data flow library now adds intermediate nodes when data flows out of a function via a parameter, in order to make path explanations easier to follow. The intermediate nodes have the same location as the underlying parameter, but must be accessed via `PathNode.asParameterReturnNode` instead of `PathNode.asNode`. `@kind path-problem` queries may have their expected test-output changed as a consequence.