feat: Create questline backend functionality

[Daanish-Khan]

• Quests are now loaded upon graph load and updates with certain actions (connect/disconnect, graph loading, node completion)
• Tasks are chosen based on current questline (ready, is apart of questline), and can be shared across quests
• Available getters and setters: -> getCurrentTasks(): gets current task list for current questline -> getCurrentQuestline(): gets current questline parent node -> setCurrentQuestline(): sets questline by id and updates currentTasks -> getAllQuests(): gets all avalable questlines