This commit changes the stream settings UI for adding subscribers to
use our standard user pills in the input box, rather than just
plain-text email addresses. This is important progress towards
removing display email addresses from the Zulip UI.
It also allows subscribing multiple users at the same time, which is a
nice improvement.
Commit 68335d9124 removed the ability to tab
into this field, since it was a hidden field. This field is no longer
hidden, and this commit restores the ability to tab into it.
sahil839
Puneeth Chaganti
Tim Abbott
Anders Kaseorg