Add missing page template

internal/templates/page.html

@@ -0,0 +1,14 @@
+{{define "content"}}
+  <article class="grid">
+    <div>
+      {{ .Content }}
+      <hr />
+      <footer class="container">
+        This is a <a href="https://twt.social">Twt.Social</a> pod.
+        If you would like your own pod, please contact <a href="https://twt.social/support">support</a>.
+        ::
+        <a href="https://github.com/jointwt/twtxt/edit/master/internal/pages/{{ .Page }}.md">Edit on github</a>
+      </footer>
+    </div>
+  </article>
+{{ end }}