Document responses API implementation

Author: thekid

ChangeLog.md

@@ -3,6 +3,14 @@ OpenAI APIs for XP ChangeLog
 
 ## ?.?.? / ????-??-??
 
+## 0.9.0 / ????-??-??
+
+* **Heads up:** To use streaming with the legacy completions API, you
+  need to use *flow()* instead of *stream()*!
+  (@thekid)
+* Merged PR #21: Implement responses API streaming, see issue #20 and
+  https://platform.openai.com/docs/api-reference/responses
+  (@thekid)
 * Added optional parameter *timeout* to receive() and transmit() methods
   (@thekid)