Where it starts: channels, direct messages and threads

This changelog starts with the messenger at Teletype's heart: channels, public and private, direct messages, one to one and in groups, and threads under any message.

Around them: mentions, reactions and pins; saved messages, reminders, drafts and scheduled sends; user groups you mention at once, guests from outside the company, your own emoji, a status for everyone and search across it all. Everything since was built on top of it.