Add an option to fetch the content of articles from sources set to "load full content" when syncing

[vosian]

Is your feature request related to a problem? Please describe. Using the program while offline will make articles from sources marked as "load full content" appear empty, as the content is fetched when the article is clicked and not when it's retrieved, unlike full text rss.

Describe the solution you'd like Have an option per source where we can specify whether to get the content when the article is detected, rather than having to wait for us to click on it.

[jstride]

Another use case is for feeds (such as reddit) that only have a link in the main body content so you always have to load the full content so it's an extra step for specific feeds.