[Feature] Directly add channel to channel group

[lonix1]

Checklist

• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• I have read the FAQ and my problem isn't listed.
• I'm aware that this is a request for NewPipe itself and that requests for adding a new service need to be made at NewPipeExtractor.
• I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

Directly add a channel to a channel group.

Why do you want this feature?

Suppose one has hundreds of channels. To add a channel to a channel group, one must

• long press channel group
• select "select subscription"
• scroll through hundreds of channels, find the one, choose it, press ok, press ok

Hunting for the channel this way takes a long time and the UI is slow to scroll, so it's difficult and a nuisance.

It would be nicer to do it the other way round:

• long press channel
• choose "add to channel group"
• select channel group, press ok

Much easier, much quicker.

Additional information

Thanks.

[SameenAhnaf]

#3353