Add CTAs to daily emails

Add a daily email CTA node type and reference field to attach a CTA to a
daily email.

Also update the RSS feed view to include the referenced body field
value.

config/sync/core.entity_view_display.node.daily_email.rss.yml

@@ -5,6 +5,7 @@ dependencies:
   config:
     - core.entity_view_mode.node.rss
     - field.field.node.daily_email.body
+    - field.field.node.daily_email.field_daily_email_cta
     - node.type.daily_email
   module:
     - layout_builder
@@ -27,4 +28,5 @@ content:
     weight: 0
     region: content
 hidden:
+  field_daily_email_cta: true
   links: true