Book Battles

See:
https://docs.google.com/document/d/1Ddeg-fWWZ0iCFzVtZR0yGY_vCPttIUrd4tCIWwvYj6g/edit#heading=h.hwsgbba3g9bn

### Describe the problem that you'd like solved

OpenLibrary.org is a catalog of millions of books, which can make finding the best books challenging. A traditional approach is to give books star ratings or reviews, but (a) this creates floating point in space and (b) many books may have 5 star ratings so this gives readers a limited understanding of whether one book is better than another. Book Battles is a way for readers to collaboratively surface the best books by voting that one book may be better than another.

### How does it work?
A reader adds books that they’ve read to the “[Already Read](https://openlibrary.org/people/mekBot/books/already-read)” shelf of their Reading Log. The reader then selects two books from their [Already Read](https://openlibrary.org/people/mekBot/books/already-read) shelf and creates a Book Battle. The reader chooses one of these two books to be the winner and optionally enters a short review explaining why.

### Proposal & Constraints

### Additional context

### Stakeholders