Allow the creation of unofficial YouTube playlists

### Description

I would like an extension of the current "videos" widget to allow for custom YouTube playlists to be created.

This is the general format: `https://www.youtube.com/watch_videos?video_ids=ID1,ID2,ID3,ID4...`

An example:

```yaml
- type: videos
title: Videos to Catch Up On
style: grid-cards
collapse-after-rows: 3
limit: 36
playlists:
- PL8mG-RkN2uTyZZ00ObwZxxoG_nJbs3qec
- 9eDLUELE-BM,dQw4w9WgXcQ,Izy88EK1dk8
```

I'd like a way to take a bunch of videos I'm interested in and put them in a section on the page to catch up on. I don't use YouTube with an account, otherwise this would just be a matter of creating a playlist from those videos. I don't see any downsides.