Channel Sidebar Organization (Post GA)

Epic for the Channel Sidebar Design and Implementation.

Goal: Channel sidebar should enhance productivity by making it as easy as possible for users to find their desired channels of communication.

User Stories: https://docs.google.com/document/d/17Uw_HMptsXADgganXffjB1k8_WuAn5nyOU5JrqZj_AA/edit#bookmark=id.1jcso4f97xz0

Competitor research:
1. https://docs.google.com/document/d/1Z1-JTAnGpkvvu8xYRb79HxUdswR_0WOIThSRaJ3dE5o/edit#bookmark=kix.sau18l3z5h0x
2. https://projects.invisionapp.com/share/Z3MD2M6B9SY

Analysis on options considered for wireframing: https://docs.google.com/document/d/1Z1-JTAnGpkvvu8xYRb79HxUdswR_0WOIThSRaJ3dE5o/edit#heading=h.gy3jry6mbv00

WIP - Initial Wireframes: https://projects.invisionapp.com/share/DYN4UDKEZPK