Time Limit for RSS Feeds

### Description

I use RSS Feeds to keep up with all of my news, but the limit function for the number of items I think could be improved by offering an alternative based on time. Some days more news happens than other days, so if a 30 article limit is set, it could account for the last 8 hours or the last 6 months depending on the feed used. I'd like if there was a property called time-limit for this case.

```
- type: rss
title: News
style: horizontal-cards
time-limit: 7d # ex. 12h or 3d
feeds:
- url: https://feeds.bloomberg.com/markets/news.rss
title: Bloomberg
```

This would allow for getting the news for the last x amount of time that the user wants to catch up on instead of a rigid number of articles total.