docs: add missing traffic-split stream plugin to config.yaml.example

[NewMayur]

The example configuration file (conf/config.yaml.example) was missing the traffic-split plugin under the stream_plugins section.

Changes

1. conf/config.yaml.example: Added - traffic-split # priority: 966 to the stream_plugins list.
2. Preserved the file's descending priority order by inserting it between mqtt-proxy (1000) and prometheus (500).
3. Files Modified => conf/config.yaml.example
4. Verified the YAML syntax using PyYAML to ensure no indentation or formatting regressions were introduced.