docs: Clarify first level URL generation

Author: integrii

docs/content/content/organization.md

@@ -28,6 +28,8 @@ in Hugo and is used as the [section](/content/sections/).
 
     .
     └── content
+        └── about
+        |   └── index.md  // <- http://1.com/about/
         ├── post
         |   ├── firstpost.md   // <- http://1.com/post/firstpost/
         |   ├── happy
@@ -41,6 +43,8 @@ in Hugo and is used as the [section](/content/sections/).
 
     .
     └── content
+        └── about
+        |   └── index.md  // <- http://1.com/about/
         ├── post
         |   ├── firstpost.md   // <- http://1.com/post/firstpost.html
         |   ├── happy
@@ -57,6 +61,9 @@ that works to organize your source content is used to organize the rendered
 site. As displayed above, the organization of the source content will be
 mirrored in the destination.
 
+Notice that the first level `about/` page URL was created using a directory
+named "about" with a single `index.md` file inside.  
+
 There are times when one would need more control over their content. In these
 cases, there are a variety of things that can be specified in the front matter
 to determine the destination of a specific piece of content.