[Cloudinary] Image URL in Editor preview broken with output_filename_only option

**Describe the bug**
When using the Cloudinary Media Library integration, I want to use the `output_filename_only` option to take advantage of URL transformations. However, this option seems to break the rendering of the preview images.

**To Reproduce**
Switch Cloudinary image assets to `output_filename_only` and observer the broken image links in the editor.

**Expected behavior**
We would expect the editor preview components to build the preview URL for the image to append the the image filename.

**Screenshots**

**Applicable Versions:**
Netlify CMS 2.3.0

**CMS configuration**
https://gist.github.com/ksherman/cb5b319858b8ea06fbf638818f839d84.js

**Additional context**
You all are awesome and I know this feature was juuuuust released :D