Suggestion: Adding a `contentType` property to `entry`

[sammibajrami]

I'm thinking something like this:

<entry>
...
  <contentType>ComicBook</contentType>
...
</entry>

The reason would be to allow reading applications to know what sort of content it is supposed to display.
For example, a PDF file can be both a novel and a comic book, and having which it is be explicitly stated could help developers make a smoother reading experience.

It could even be used to expand the standard to support things like audio-based podcast episodes or video-based learning courses.