We add a popover on click which allows user to create or browse
streams too.
Reason for doing so:
At present, it is hard to discover how to join streams
and create new streams. In particular:
Users have a hard time finding the gear in the STREAMS
header in the left sidebar and realizing that it's relevant for them.
Even once a user is in the STREAMS menu, the Create
stream button is hard to spot.
Fixes#18694.
4b4fdad0e3