Review mobile unread toast behaviour

Description

Toast notification that allows easily jumping to the latest messages when entering a channel with many unreads.

Spec doc: https://docs.google.com/document/d/1lANE8O3jVn4yjHNBbe4tMtXVcl3BYcRLWS0IViQ2Vds/edit

Invision design: https://projects.invisionapp.com/share/Q9RFOJFDMSW#/screens/368904975

QA Test Steps

No testing required.

Reporter

None

Mana

2

Assignee

Andrew Brown

QA Assignee

None

Reporter

Eric Sethna

Epic Link

None

Fix versions

Mattermost Team

UX

Sprint

None

Labels

QA Testing Areas

None

GitHub Issue

None

Components

None
Configure