add bytecode Effect issue

Author: jmid

README.md

@@ -321,6 +321,12 @@ In `STM` a functor `STM.AddGC` is also available. It inserts calls to
 Issues
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+Bytecode interpreter can segfault on unhandled `Effect` (new, fixed)
+--------------------------------------------------------------------
+
+In seldom cases the tests would [trigger a segfault in the bytecode interpreter when treating an unhandled `Effect`](https://github.com/ocaml/ocaml/issues/11669)
+
+
 `Ephemeron` can fail assert and abort (new, open)
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