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/field.field.node.daily_email.field_daily_email_cta.yml

@@ -0,0 +1,29 @@
+uuid: 115fb0c0-03eb-43b1-8b89-3740b2645160
+langcode: en
+status: true
+dependencies:
+  config:
+    - field.storage.node.field_daily_email_cta
+    - node.type.daily_email
+    - node.type.daily_email_cta
+id: node.daily_email.field_daily_email_cta
+field_name: field_daily_email_cta
+entity_type: node
+bundle: daily_email
+label: CTA
+description: ''
+required: false
+translatable: false
+default_value: {  }
+default_value_callback: ''
+settings:
+  handler: 'default:node'
+  handler_settings:
+    target_bundles:
+      daily_email_cta: daily_email_cta
+    sort:
+      field: title
+      direction: ASC
+    auto_create: false
+    auto_create_bundle: ''
+field_type: entity_reference