Add HTML slides link

Fixes #222

config/default/field.field.node.talk.field_slides_html.yml

@@ -0,0 +1,23 @@
+uuid: 5a9576e0-0130-46ba-9ebf-75609d617af8
+langcode: en
+status: true
+dependencies:
+  config:
+    - field.storage.node.field_slides_html
+    - node.type.talk
+  module:
+    - link
+id: node.talk.field_slides_html
+field_name: field_slides_html
+entity_type: node
+bundle: talk
+label: 'HTML slides'
+description: 'Add a link to the HTML slides, if there are some.'
+required: false
+translatable: false
+default_value: {  }
+default_value_callback: ''
+settings:
+  link_type: 16
+  title: 0
+field_type: link