Updates to the newsletter flow

Create the emails as a draft,

The old design had the email and the scheduling all on the same screen, I've split this into two screens now.

The email screen now lets you focus on crafting the email you want to send. I do have to find a space for the edition number but I'm tempted to add that to the Schedule screen.

The preview option is available on the email screen, so it will send you the email for you to review and make sure it's ok.