✨ Add 'Editor' page that's used to submit candidate passages

[r002]

Specs:

• A candidate passage is always in the context of a storyId and a parentPassageId.
• A story is a chain of passages that have graduated from candidate status to cannon status.
• For every story, there can only be one cannon?

GUI:

• For each passage candidate, specify its parentPassageId -- this also automatically then sets its storyId.