feat(custom message): add a generic way to add a custom message in pages

src/partials/article.hbs

@@ -24,12 +24,18 @@
   {{#if page.attributes.next-release}}
   <div class="paragraph next-release-block">
     <p>This content is dedicated to our next version.
-    It is work in progress: its content will evolve until the new version is released.
-    Before that time, it cannot be considered as official.
+      It is work in progress: its content will evolve until the new version is released.
+      Before that time, it cannot be considered as official.
     </p>
   </div>
   {{/if}}
 
+  {{#if page.attributes.custom-message}}
+  <div class="paragraph next-release-block">
+    <p>{{page.attributes.custom-message}}</p>
+  </div>
+  {{/if}}
+
   {{#with page.title}}
   <h1 class="page">{{{this}}}</h1>
   {{/with}}