Add Reader templates

[umerfaruk]

Add reader templates. For example a kids books is written in bigger fonts and with more line and character spacing for easier reading. Possible themes can be:

Normal

This is the theme for normal reading with wide pages and less space between lines

Magazine

This is the theme for magazine style reading where the page is not very wide and the space between lines in normal.

Kids

This theme is for easy reading. The font size is bigger and the distance between lines in greater.