User Onboarding - Upload Profile Image Component

[ErisDS]

This is part of the User Onboarding epic: #5315

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Both the signup, and setup screens feature this new upload component:

It comprises both a small circular thumbnail image, and an email input. When you enter an email, if it matches a gravatar, the gravatar image is pulled in:

If you mouseover the image, you'll see an overlay with the upload icon appearing:

Clicking on this icon/overlay should open a file dialog to trigger an image upload. Dragging an image to the icon/overlay should also trigger an upload. There should be no intermediary modal as we currently have for uploads in the admin UI.

The hierarchy here is that the Ghost logo shows (but is not used as the user's image) until either a gravatar image is loaded via the email, or an image is uploaded. An uploaded image always takes precedent over a gravatar image, even if a new email address is entered.

The behaviour for fetching the gravatar is hardcoded into the setup screen as of the PR #5316. This needs to be broken out into a reusable component. The image upload behaviour is currently completely missing.

The ideal here would be to build a flexible new upload component in ember, that can be optionally tied to an email field in order to layer the gravatar behaviour in as well. Bonus points if the image uploader uses blueimp's preview feature to display the image whilst it is being uploaded in the background 😉