Reference Storage Rework - 4pts

[jakedcolbert]

• Separate the current reference store into two stores: current and next.
• Use the next store to update dropdown labels mid navigation.
• navbar label should update to what the user selects in real time and then either:
  • Navigate to new reference on navigation completion
  • Abandon navigation and revert to current reference on navigation cancel

[chrisvire]

I think you can leave the current group store for now and just implement a navRef which is the current navigation state. We determined that we can use the referenceStore type for this since is always defaults to a valid reference. So it will have to be a store with just an object like:

export const navRef = writable({ book: '', chapter: '' });