Add call status indicator when adding new participant to a conf

Refer to https://www.sketch.com/s/f15c7123-d06a-4e8f-96ab-3c0f58ad99c6/p/5a8874fe-ec8e-4274-a67d-5c23093e05a5

added to epic &31 (closed)

changed the description

assigned to @mzhang

added SprintTo review label

mentioned in commit 77aae847

removed SprintTo review label

closed