Modernize placement of post list page and add some comments.

By modernize I mean that Hugo formerly used the "section/section"
scheme, but now we can put all related section templates in one folder.

Also, more commenting!

layouts/section/post.html → layouts/post/list.html

@@ -1,12 +1,17 @@
 {{ define "main" }}
+{{/*
+  This template is the same as the default and is here to demonstrate that if you have a content directory called "post" you can create a layouts directory, just for that section.
+   */}}
   <article class="pa3 pa4-ns nested-copy-line-height nested-img">
   <main class="cf ph3 ph5-l pv3 pv4-l f4 tc-l center measure-wide lh-copy mid-gray">
     {{ .Content }}
   </main>
-    {{ $section := .Paginate (where .Data.Pages "Section" .Section) }}
     <section class="flex-ns flex-wrap justify-around mt5">
-      {{ range  $section.Pages }}
+      {{ range  .Pages }}
         <div class="relative w-100 w-30-l mb4 bg-white">
+          {{/*
+          Note we can use `.Render` here for items just in this section, instead of a partial to pull in items for the list page. https://gohugo.io/functions/render/
+          */}}
           {{ .Render "summary" }}
         </div>
       {{ end }}