[457] - Immersive reading view

[TheRealAnt]

Fixes #457

• Hiding bars when scrolling down WebView & showing when scrolling up.
• Showing bars when device rotates into landscape mode.

Demo:

https://github.com/kiwix/kiwix-apple/assets/22860503/8eaa3a49-779a-4fec-93ff-8147af110526

[kelson42]

It‘s important to check that his fox has no unwanted side effect on macOS (iPadOS?)

[kelson42]

@TheRealAnt I like that the feature is implemented with so few lines of code

[BPerlakiH]

@TheRealAnt Currently your changes are limited to iOS / iPad OS only, so they have no effect on macOS, which is good. There's one thing I noticed immediately, that it also applies the bar hiding on iPad OS, which is something we did not wanted. On iPad there are multiple things that can affect the amount of scroll needed to display the content: side bar collapsing, split screen mode and so on. My suggestion is to keep these changes limited to iOS only for now. iPad screens are already large enough, plus as we discussed earlier, there's only 1 bar on iPad: