Missing documentation about oembed in Redactor->CKEditor

[KevinBodi]

Description

Redactor used <iframe>-tags for embedding while CKEditor uses a <oembed>-tag. When a site supports embedding in their rich text editors existing embeds that were in the database before migrating will also work as supposed after migrating, but when using CKEditor to add new embeds it won't render without any extra configs to make it work.

I suppose there is some extra work that must be done to make this work, that isn't described in the documentation. Edit: We needed iframely or Embedly installed in the frontend

Steps to reproduce

1. Migrate from Redactor to CKEditor
2. Use the rich text editor to add new embeds after migrating
3. The embed or video doesn't appear when it used to do so in Redactor