Multiple RTSP stream support pushed to dev release

[tphakala]

Support for multiple RTSP streams is now implemented, code is tested only very lightly so I would request you to test and provide feedback, feature is currently available for github source code and docker dev builds.

Each RTSP stream is configured with defining --rtsp cli flag multiple times

docker run -ti -p 8080:8080 ghcr.io/tphakala/birdnet-go:dev realtime --rtsp url_for_stream1 --rtsp ulr_for_stream2

[tphakala]

There was important fixes and improvements to this in PR #188, this lays important groundwork for supporting multiple audio sources regardless of type.