Section-wise theme/display customisation

[PlytonRexus]

Each section can have its own styling. We can consider the following as minimum requirements:

1. separate backgrounds (if desired)
2. separate stats bar positioning/hiding
3. Fonts/colours

In a gist, each section should have its own theme. If the writer does not supply one, it should be inherited from the story's default.
One section can look like a page from an ancient tome, while the other can look like the console out of a sci-fi movie.