Add Send to social media checkbox to posts

Also add it to the `opdavies_blog_test` module config so that the
existing tests continue to work and pass.

References #249

config/default/core.entity_view_display.node.post.teaser.yml

@@ -10,6 +10,7 @@ dependencies:
     - field.field.node.post.field_has_tweet
     - field.field.node.post.field_images
     - field.field.node.post.field_note
+    - field.field.node.post.field_send_to_social_media
     - field.field.node.post.field_sent_to_social_media
     - field.field.node.post.field_series
     - field.field.node.post.field_tags
@@ -40,6 +41,7 @@ hidden:
   field_has_tweet: true
   field_images: true
   field_note: true
+  field_send_to_social_media: true
   field_sent_to_social_media: true
   field_series: true
   field_tags: true