Add compatibility for .MOBI File Format.

[MonotoneDevelopment]

The .MOBI file format has already been reverse engineered multiple times, and seeing that this is a multipurpose reader, it should be able to easily compensate for the lack of support.

The best source I could find on designing a reverse-engineering tool is here:

https://wiki.mobileread.com/wiki/MOBI

Please make this a feature for compatibility, thanks