Issue

After last changes (downloading images, generating epub etc) processing all sources can take long time and blocks the Koreader until finished.

How about quick option in menu - could be an item/"button" in Newsdownloder
menu "(toogle?) images download"
which will override defualt "download images" settings from feed_config.lua.

This menu item could display current downloading status:
"Images download : off" -> click on reverses to "on"
"Images download: on" -> click on reverses to "off"

This can be "global" option that enables download images only for feeds which have " include_images=true" in feed_config.lua. Shouldn't donwload images for other feed sources.

Can be useful when you're just about to leave home and have no time for full downloading all news with images and processing to epub.