[Feature Request] Side-by-side / two-page view in reader

[tylercamp]

Is your feature request related to a problem? Please describe. Some manga is structured like a book where a single scene can span two pages. For big scenes, the current presentation of only one page can be confusing or distract from the scene as a whole.

Describe the solution you'd like I'd like a toggle option in the "Paged" mode to enable "Side-by-Side" view.

It should also have:

• A toggle for offsetting the 2-page grouping by one, in case the manga doesn't provide a blank first page to align them. (eg Expected view has page 1 as one full page group, and pages 2 and 3 make another full page group. Without an offset option, it would incorrectly group pages 1 and 2.)
• Interaction with the "right-to-left" toggle setting, since that affects (reverses) the displayed ordering of a 2-page group

Since this configuration is guaranteed to be constant for any given manga (eg any users with side-by-side view will always end up with the same offset and RTL options) it would be extra convenient for this to either save automatically as metadata for the chapter, or have an option for admin users to save it as a default for other users.

[Leeingnyo]

Thanks for suggestion! This looks helpful to resolve https://github.com/hkalexling/Mango/issues/5 too.