Enhancement: Ability to add a default image per collection.

[nat-alt]

For example, in a blog collection, we often reference {{ feature_image }}.

We currently have a global fallback image, or a specific image set on each entry, but it would be helpful to define a default field for the entire collection.

Can currently achieve with something like this in tjhe layout:

{{ if collection == "blog" }}
  {{ unless alt_seo_social_image }}
    {{ alt_seo_social_image = feature_image }}
  {{ /unless }}
{{ /if }}

But would be good to be able to configure from admin.

[benmAltDesign]

Just an admin note, I need to investigate if extending collection data is now supported in Stat 6.

Versions below 6 didn't provide the ability to augment the fields in a collection and would've required something less ideal but that may be a path forward if Statamic 6 does not that feature