UX: add information about the use of permalinks

app/assets/javascripts/admin/templates/permalinks.hbs

@@ -1,6 +1,9 @@
 <div class="permalink-title">
   <h2>{{i18n 'admin.permalink.title'}}</h2>
 </div>
+<div class="permalink-description">
+  <span>{{i18n 'admin.permalink.description'}}</span>
+</div>
 <div class="permalink-search">
   {{text-field value=filter class="url-input" placeholderKey="admin.permalink.form.filter" autocorrect="off" autocapitalize="off"}}
 </div>

app/assets/stylesheets/common/admin/customize.scss

@@ -613,6 +613,10 @@
   margin-bottom: 10px;
 }
 
+.permalink-description {
+  color: dark-light-choose($primary-medium, $secondary-medium);
+}
+
 // embedding
 .embeddable-hosts {
   margin-bottom: 2em;

config/locales/client.en.yml

@@ -4265,6 +4265,7 @@ en:
 
       permalink:
         title: "Permalinks"
+        description: "Please note this will only work for redirecting external links, it will not work for internal links."
         url: "URL"
         topic_id: "Topic ID"
         topic_title: "Topic"