feat(netlify-cms-widget-list): allow 'summary' field (#3616)

website/content/docs/beta-features.md

@@ -163,6 +163,7 @@ To use variable types in the list widget, update your field configuration as fol
 
 - `types`: a nested list of object widgets. All widgets must be of type `object`. Every object widget may define different set of fields.
 - `typeKey`: the name of the field that will be added to every item in list representing the name of the object widget that item belongs to. Ignored if `types` is not defined. Default is `type`.
+- `summary`: allows customization of a collapsed list item object in a similar way to a [collection summary](/docs/configuration-options/?#summary)
 
 ### Example Configuration
 
@@ -177,6 +178,7 @@ either a "carousel" or a "spotlight". Each type has a unique name and set of fie
     - label: 'Carousel'
       name: 'carousel'
       widget: object
+      summary: '{{fields.header}}'
       fields:
         - { label: Header, name: header, widget: string, default: 'Image Gallery' }
         - { label: Template, name: template, widget: string, default: 'carousel.html' }

website/content/docs/widgets/list.md

@@ -12,6 +12,7 @@ The list widget allows you to create a repeatable item in the UI which saves as
   - `default`: if `fields` is specified, declare defaults on the child widgets; if not, you may specify a list of strings to populate the text field
   - `allow_add`: if added and labeled `false`, button to add additional widgets disappears
   - `collapsed`: if added and labeled `false`, the list widget's content does not collapse by default
+  - `summary`: allows customization of a collapsed list item object in a similar way to a [collection summary](/docs/configuration-options/?#summary)
   - `field`: a single widget field to be repeated
   - `fields`: a nested list of multiple widget fields to be included in each repeatable iteration
 - **Example** (`field`/`fields` not specified):
@@ -34,6 +35,7 @@ The list widget allows you to create a repeatable item in the UI which saves as
     - label: "Gallery"
       name: "galleryImages"
       widget: "list"
+      summary: '{{fields.image}}'
       field: {label: Image, name: image, widget: image}
     ```
 - **Example** (with `fields`):
@@ -41,6 +43,7 @@ The list widget allows you to create a repeatable item in the UI which saves as
     - label: "Testimonials"
       name: "testimonials"
       widget: "list"
+      summary: '{{fields.quote}} - {{fields.author.name}}'
       fields:
         - {label: Quote, name: quote, widget: string, default: "Everything is awesome!"}
         - label: Author