docs(changelog): add entry for screenVideo destination support

changelog/4370.added.md

@@ -0,0 +1,16 @@
+- Added support for Daily's built-in `screenVideo` destination in `DailyTransport`. When `"screenVideo"` is included in `video_out_destinations` transport parameter, a dedicated screen video track is created at join time and frames with `transport_destination="screenVideo"` are routed to it.
+
+  ```python
+  params = DailyParams(
+        video_out_enabled=True,
+        video_out_is_live=True,
+        video_out_width=1280,
+        video_out_height=720,
+        video_out_destinations=["screenVideo"]
+  )
+
+  ...
+
+  frame = OutputImageRawFrame(...)
+  frame.transport_destination = "screenVideo"
+  ```