docs: add changelog for #31

Author: markbackman

changelog/31.fixed.md

@@ -0,0 +1 @@
+- Fixed deprecation warnings being emitted for every frame sent to Whisker. Deprecated frame fields, such as `StartFrame.audio_in_sample_rate` and its siblings, warn when read, and the serializer read each dataclass field twice while walking every frame. It now reads the raw instance state instead, so no warning is emitted.