Add option for the image widget to return object instead of URL

**Is your feature request related to a problem? Please describe.**
The image widget returns a string (URL) or an array of strings if `multiple: true`. On Cloudinary you can have much more data from that image, but we can't get that to the CMS.

**Describe the solution you'd like**
I would like to see an option to return an object that would return also some metadata about the image. I am mostly interested in alt and title, but other fields could be added too.

Example
```yaml
{label: Featured Image, name: image, widget: image, media_library: {config: {
multiple: true,
return_object: true
}}},
```

another option would be to add more control - let's say we define an array of fields that we want returned
```yaml
{label: Featured Image, name: image, widget: image, media_library: {config: {
return_fields: [url, title, alt, created_at]
}}},
```

**Describe alternatives you've considered**
Now you have to create your own object with alt and title fields, and that could mean double work and double data.