Earn XP, coins, and Critters for reaching milestones in a book

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As David, I would like to earn XP and coins for reaching milestones while reading my books.

Tasks

• Once a user completes a chapter within a book, display a message that the user has gained x amount of XP and y amount of coins, and if they earned a new Critter
• Update the user's XP, coins, and Critter collection in the database

Acceptance criteria

• Users should see that they've gained XP, coins, and maybe Critters once they complete a chapter in a book
• A user's entry in the database should be updated with their new amount of XP, coins, and critters