Track quests and milestones

[kyleshay]

There are some quests that are account-wide that you can not track with the API because there isn't an instance ID, it would be nice to DIM-track them.

Additionally, tracking normal quest-items (steps) with instance ids by their parent quest would be nice so when you complete a quest step in-game, DIM is still tracking the questline.

[kyleshay]

Adding that it would be nice to add milestones to track as well