Feature request: option to make PRISMA statement horizontal

[M-Colley]

Hi there, I really like the package, it provides an easy way to generate the PRISMA statement.

I would like one extra layout feature:

Instead of making the "flow chart" vertical (top to bottom), would it also be possible to include an option to make it horizontal (from left to right)?

This would help scientists make use of the spare space better, depending on the layout of the paper.

Thank you for your consideration!