Slack-like browser icon change behaviour for DND mode
In Slack, if the current user mode is DND, there are three types of browser tab icon:
1) The normal icon when there is nothing new in the team chat.
2) The white icon when there are some new messages in some channels.
3) The red icon when there are some new messages with mentions or in the user private channel.
It would be nice to have the same behaviour so that the user in DND mode can avoid notifications but react accordingly based on tab icon.