Create a Shared Realtime Checklist

Our mission is to create a shared checklist (_or "Todo list" if you prefer_) we can all see and update in realtime.

+ [x] `mix phx.new app`
+ [x] create schema for checklist item:
+ [x] title
+ [x] status
+ [x] priority
+ [x] time_estimate
+ [x] deadline
+ [x] schedule
+ [x] assignee
+ [x] owner

+ [x] add a few records
+ [x] sort by priority

# Status

+ [x] use ecto_enum https://github.com/gjaldon/ecto_enum for **`status`** to only allow a set of options:
+ [x] unassigned - the task is created but nobody is assigned to work on it.
+ [x] assigned - assigned to a specific person but they are not yet working on it
+ [x] in_progress - assignee is working on the task
+ [x] awaiting_review - person who worked on the task assigned it back to the owner for review
+ [x] in_review - owner (or "QA") is reviewing the task for completion
+ [x] complete - owner marked as complete
+ [x] dependent - dependent on another task or person
+ [x] blocked - progress cannot continue https://github.com/dwyl/labels/issues/87

+ [x] display the status as a dropdown
+ [x] apply status `:assigned` if `assignee` is set

# Channel `#5`

+ [ ] create channel for sending realtime updates to connected viewers