Add support for embedded images

[roya0045]

Greetings,

I'm not sure if it worth implementing but here is a potential improvement: In some instances documentation is self contained in a single database, and children have images as blob. Currently as QImageReader is the class code handling images, there's no way to retrieve images stored in a database.

Personally my solution is to display the image with some formatting and interaction with html widgets, but maybe users of this plugin would like support for those data sources without having to make a bespoke widget to view them, as your plugin already supports viewing images in its widget.