[web] Add sidebars to activeChatThreadItem

Summary: activeChatThreadItem had no sidebars included and they were not displayed in chat-thread-list if this thread was not in chatListData.

Test Plan: Open activeChatThreadItem that is not in chatListData and see sidebars user is member of displayed below active thread

Reviewers: palys-swm, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, zrebcu411, Adrian, atul, subnub

Differential Revision: https://phabricator.ashoat.com/D946