examples(foundational): move 15/15a logic into its own processor

CHANGELOG.md

@@ -5,6 +5,14 @@ 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
+
+### Other
+
+- Updated `15-switch-voices.py` and `15a-switch-languages.py` examples to show
+  how to enclose complex logic (e.g. `ParallelPipeline`) into a single processor
+  so the main pipeline becomes simpler.
+
 ## [0.0.79] - 2025-08-07
 
 ### Changed