[Feature request] [5.0b2] Add channels to feed group while viewing that feed group

[91grayjay]

Checklist

• [x] I have searched for existing issues (open and closed) and confirmed this feature hasn't been requested before
• [x] I believe this feature request will benefit more than 10% of users, not just myself

Feature Description

Currently as far as I can find, you can only add a channel to a feed group by going to the channel page on pipepipe 5.0b2 and press the + icon besides subscribe button.

This is fine for unsubscribed channel I suppose, but if you're new to pipepipe and have no import data, going to each channel to add it to feed groups one by one is tedious.

I propose so you can go to the feed page and add your subscribed channels to that feed from the feed view.

Or Or add channels to feed group like in version 4.7.4