feat: Added page to template context.

defaults/layouts/page.html

@@ -2,7 +2,7 @@
 {{$main}}
 <main>
   <article>
-    <h1>{{page_title}}</h1>
+    <h1>{{page.title}}</h1>
     {{#date_iso}} <time class="subtitle" datetime="{{date_iso}}">{{date_display}}</time>
     {{/date_iso}} {{&content}}
   </article>

defaults/layouts/section_index.html

@@ -1,7 +1,7 @@
 {{<base}}
 {{$main}}
 <main>
-  <h1>{{page_title}}</h1>
+  <h1>{{page.title}}</h1>
   {{&content}}
   {{#posts | group_by year}}
   <section>