services: added new DeepgramSTTService

CHANGELOG.md

@@ -5,6 +5,16 @@ All notable changes to **pipecat** will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Changed
+
+- Added `DeepgramSTTService`. This service has an ongoing websocket
+  connection. To handle this, it subclasses `AIService` instead of
+  `STTService`. The output of this service will be pushed from the same task,
+  except system frames like `StartFrame`, `CancelFrame` or
+  `StartInterruptionFrame`.
+
 ## [0.0.29] - 2024-06-07
 
 ### Added