Minor change to tutorial part four index.md (gatsbyjs#3649)

* Minor change to tutorial part four index.md

Changed one liner 2 steps to <ol> style.
More readable.

* Update index.md

Author: danielemesh

docs/tutorial/part-four/index.md

@@ -733,8 +733,10 @@ you use GraphQL to query your _data_ and _map_ the data to _pages_—all at buil
 time. This is a really powerful idea. We'll be exploring its implications and
 ways to use it for the remainder of the tutorial.
 
-Creating new pages has two steps, 1) generate the "path" or "slug" for the page
-and 2) create the page.
+Creating new pages has two steps:
+
+1. Generate the "path" or "slug" for the page.
+2. Create the page.
 
 To create our Markdown pages, we'll learn to use two Gatsby APIs
 [`onCreateNode`](/docs/node-apis/#onCreateNode) and