[FR]: Specific option: "Auto-fetch all feeds for selected feed categories every: X minute(s) and X second(s)"

[RetroAbstract]

Brief description of the feature request

As the title says, this specific option would allow the user to set RSSGuard to auto-fetch all feeds to selected feed categories every: X minute(s) and X second(s).

This option would have a menu where the user can add & remove feed categories to include in the auto feed fetching of selected categories every: X minute(s) and X second(s).

Would be located in: Tools > Settings > Feeds & Articles > Feed Fetching