Add setting for sidebar location

[WiseFerret]

I use foliate with an RTL user interface (Hebrew). That means that the sidebar, containing the booktable of contents, is always displayed to the right of the main text. When the e-book is in English, this becomes inconvenient. I have no way of moving the side bar to the left, except starting foliate with export LANG=C (and then, of course, the interface is not translated).

The most straight forward solution is to add a user setting regarding the location of the sidebar: left or right.

An alternative solution is to detect the language of the e-book, and set the location of the sidebar accordingly. But this might be unreliable and more difficult to program.

[johnfactotum]

The current behavior is acceptable in my opinion.

But probably we could just make the UI follow the page progression direction. That would make sense if one sees the chrome as an extension of the book. The one problem is that when you click on the Library button, the view would appear to slide in the wrong direction.

[WiseFerret]

Adjusting the UI to the page progression direction sounds ideal to me. Can't the sliding animation be adjusted as well accordingly?

[johnfactotum]

For the animation, see #1084 (comment)

[johnfactotum]

Ah, I misunderstood. You mean the animation between the book and the library view. Well, yes, I suppose that can be fixed.