Add all URLs shown on website to feed.json

The data gathered from feed.json != .xml file, for example feed.json of kdenlive doesn't have project url / download url but https://github.com/AppImage/appimage.github.io/blob/master/database/Kdenlive/org.kde.kdenlive.appdata.xml has it.

Every kde app like kdenlive, kdevelop or any old app available here either doesn't have project url or download url or sometimes both in feed.json.

So what I propose is that they should be either update or removed as they are very confusing, cause user will think that this app has appimage, but they will not find the project url or download url for that app.

Or provide an alternate way to fetch data instead of feed.json