In email digests, try to get longer excerpts if we don't have enough

characters from the first paragraph.

config/locales/server.en.yml

@@ -785,6 +785,7 @@ en:
 
     allow_uploaded_avatars: "Allow users to upload their custom avatars"
     allow_animated_avatars: "Allow users to use animated gif for avatars. WARNING: it is highly recommended to run the avatars:regenerate rake task after changing that setting."
+    digest_min_excerpt_length: "How many characters we're aiming for for each post in the email digest"
     default_digest_email_frequency: "How often users receive digest emails by default. They can change this setting in their preferences."
     default_external_links_in_new_tab: "Open external links in a new tab. Users can change this in their preferences."
 

config/site_settings.yml

@@ -213,6 +213,7 @@ posting:
 email:
   email_time_window_mins: 10
   email_posts_context: 5
+  digest_min_excerpt_length: 100
   default_digest_email_frequency:
     default: 7
     enum: 'DigestEmailSiteSetting'