Add archived_at option to ChannelSort

[lukewilson2002]

Motivation
There is a pinned_at property but not an archived_at to sort channels in the ChannelList by whether they have been archived. Currently I believe the only way to achieve this without forking, would be to build a custom channel list component.

Type in question: ChannelSort<DefaultGenerics>

Proposed solution
Add archived_at to channel sorting options.

See this documentation that suggests pinned_at and archived_at are very similar in proposed use, except that channels cannot be sorted by when they were archived:

https://getstream.io/chat/docs/sdk/react-native/guides/channel-pinning-and-archiving/#filtering-channels