Image Credits: no preview in the editor

[adekbadek]

Describe the bug When using an image with credits (#1147), the credits do not appear in the editor.

To Reproduce Steps to reproduce the behavior:

1. Add credit to an image
2. Insert it in a post or page
3. Observe the credit does not appear in the editor

Expected behavior The image credit should appear in the editor, just like it does on the front-end.

[laurelfulford]

@adekbadek Discussed this issue a bit -- one odd thing to consider:

When you add an image block to the editor, if it has a caption in the Media Library, it will be displayed automatically. If you edit that caption from the image block, it will display your new caption in the story, but it will not update the original caption set in the Media Library. This is helpful because you can use the same image multiple times, but craft the caption based on context (or choose not to show a caption at all in some cases).

The credit is a little different. There's not really a reason why a photo's credit should change based on context -- if shown, it should always attribute the same person. But having it behave differently could be confusing. So to add it to the editor, we'll need to consider whether it should be editable from there too:

• If not editable, how should the credit should look to make it clear it's not editable like the caption is? And should we have some directions to edit it in the Media Library?
• If editable, should editing the credit overwrite the value in the Media Library, and change it for all images? Or should it act like the caption and let you change in on a per image basis (I can't see this being needed from an editorial standpoint -- honestly it makes zero sense to change on a per image basis -- but it would be more consistent UX).