Combine hashtag, list, or other timelines into merged columns

[noamross]

This is related to an often-requested core mastodon feature request of adding hashtags to lists (https://github.com/mastodon/mastodon/issues/7692, ), and also #25. I would like the ability to create "merged" columns that combine hashtags and lists or possibly other feeds like local timelines. This would enable curating topical columns and if implemented client-side, it could be much more flexible.

[barredo]

This is a nice idea. Will think about how to best implement when I go with #25