add WSSongListRoutes.kt

- add Websocket backend.
- add session start command.
- some improve logics.

.idea/.gitignore

@@ -6,4 +6,5 @@
 # Datasource local storage ignored files
 /dataSources/
 /dataSources.local.xml
-discord.xml
+discord.xml
+inspectionProfiles/Project_Default.xml