Add ability to create 'poem' books

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As discussed in our last PH session, some classes are interested in doing a Poem in class using the app.

The layout for such stories is different in that they only require four pages: - Cover - About The Author - Poem Page - Back Page

Creating a new type of story would allow these classes to use the tool while part-taking in the Publishing House program.

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Created feature branch for this work to commence