refs https://github.com/TryGhost/Team/issues/2887
Images could sometimes be pasted into the editor (noticed especially with Google Docs) with `data:` URLs rather than typical `https:` URLs. That causes problems because data URLs are large binary blobs that get stored in the `posts` table and passed through many areas of the system that doesn't expect large binary blobs, causing knock-on effects.
- added handling to our editor's image card to detect when the card is displayed in the editor with a `data:` URL and if it was then it converts it to a file and uploads it so the image can be stored and displayed the same way as any other image
- handles uploads on both paste and opening a post in the editor that was previously saved with a `data:` URL
11cab899f0