Document breaking change

Author: dbanty

.changeset/support_ref_in_responses.md

@@ -0,0 +1,12 @@
+---
+default: major
+---
+
+# Support `$ref` in responses
+
+Previously, using a `$ref` to define a response was ignored, the code to call the endpoint was still generated, but 
+the response would not be parsed. Now, responses defined with `$ref` will be used to generate the response model, which 
+will parse the response at runtime.
+
+If a `$ref` is incorrect or uses a feature that is not supported by the generator, these endpoints will start failing to 
+generate.