Add about_extra_description option for posts.

Author: MrWillCom

.changeset/silly-news-help.md

@@ -0,0 +1,5 @@
+---
+'hexo-theme-cupertino': minor
+---
+
+Add `about_extra_description` option for posts.

layout/post.ejs

@@ -47,6 +47,7 @@
       <% }) %>
     </p>
     <% } %>
+    <% if (page.about_extra_description) { %><div class="extra"><%- page.about_extra_description %></div><% } %>
   </div>
   <% } %>
 

source/css/post.scss

@@ -301,6 +301,10 @@ body {
         margin: 6px 0;
       }
     }
+
+    & > .extra {
+      font-size: 15px;
+    }
   }
 
   #{$content} {