feat: add the ability to use Sointu as a sync-tracker

There is a new "sync" opcode that saves the top-most signal every 256 samples to the new "syncBuffer" output. Additionally, you can enable saving the current fractional row as sync[0], avoiding calculating the beat in the shader, but also calculating the beat correctly when the beat is modulated.

cmd/sointu-nativetrack/main.go

@@ -17,5 +17,7 @@ func main() {
 	}
 	defer audioContext.Close()
 	synthService := bridge.BridgeService{}
-	gioui.Main(audioContext, synthService)
+	// TODO: native track does not support syncing at the moment (which is why
+	// we pass nil), as the native bridge does not support sync data
+	gioui.Main(audioContext, synthService, nil)
 }