Show youtube streams in the videos section

### Description

At the moment you can't see livestreams by youtubers in the videos channel which is bad for me because some of the channels I have shown there almost exclusively do streams and no actual youtube videos.
I want a way of including these streams in the video section or being able to toggle per creator, which tab you want to pull from. Some of them I want just the normal videos and some of them I want the streams from, so it would be nice to be able to choose which ones I want from each creator

so for example:
```
type: videos
channels:
- [channel ID]
show-live-streams: true
```

or maybe:
`
content: livestreams, videos
`
for multiple choice

No files or tests are named. Start by locating the videos section and its YouTube channel configuration and filtering logic, then trace how per-channel options are parsed. Done means livestreams can be selected independently for each configured creator while existing video-only behavior remains available.

Written by the indexing model from the issue text.