Revert "Revert #15, since it may not actually be needed"

This reverts commit 6d39751edce7e55b1ecb3da0a420e1b4f185cf24.
diff --git a/release-notes/VERSION b/release-notes/VERSION
index 9d2fa70..4a839f2 100644
--- a/release-notes/VERSION
+++ b/release-notes/VERSION
@@ -3,6 +3,9 @@
 
 New minor version
 
+#15: Add `JsonTypeInfo.As.EXISTING` property to support new variation
+  for including Type Id.
+
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 === History: ===
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