Add websockets-base optional dependency and use for DRY pyproject.toml

CHANGELOG.md

@@ -18,7 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   async def on_pipeline_finished(task: PipelineTask, frame: Frame):
       ...
   ```
-  
+
 ### Changed
 
 - `torch` and `torchaudio` are no longer required for running Smart Turn
@@ -30,6 +30,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   usage of `ConnectionClosed.code` and `ConnectionClosed.reason` attributes in
   `AWSTranscribeSTTService` for compatibility.
 
+- Refactored `pyproject.toml` to reduce websockets dependency repetition using
+  self-referencing extras. All websockets-dependent services now reference a
+  shared `websockets-base` extra.
+
 ### Deprecated
 
 - `PipelineTask` events `on_pipeline_stopped`, `on_pipeline_ended` and