Add h3 headers

Added h3 headers to appropriate files.

content/github/getting-started-with-github/create-a-repo.md

@@ -15,6 +15,8 @@ topics:
   - Accounts
 ---
 
+### Create a repository
+
 {% if currentVersion == "free-pro-team@latest" %}
 
 You can store a variety of projects in {% data variables.product.product_name %} repositories, including open source projects. With [open source projects](http://opensource.org/about), you can share code to make better, more reliable software.

content/github/getting-started-with-github/fork-a-repo.md

@@ -16,6 +16,8 @@ topics:
   - Accounts
 ---
 
+### About forks
+
 Most commonly, forks are used to either propose changes to someone else's project or to use someone else's project as a starting point for your own idea.
 
 #### Propose changes to someone else's project

content/github/getting-started-with-github/set-up-git.md

@@ -22,6 +22,8 @@ topics:
   - Accounts
 ---
 
+### Using Git
+
 To use Git on the command line, you'll need to download, install, and configure Git on your computer. {% if currentVersion == "free-pro-team@latest" or currentVersion ver_gt "enterprise-server@2.19" or currentVersion == "github-ae@latest" %} You can also install {% data variables.product.prodname_cli %} to use {% data variables.product.product_name %} from the command line. For more information on {% data variables.product.prodname_cli %}, see the [{% data variables.product.prodname_cli %}](https://cli.github.com/manual/) documentation.{% endif %}
 
 If you want to work with Git locally, but don't want to use the command line, you can instead download and install the [{% data variables.product.prodname_desktop %}]({% data variables.product.desktop_link %}) client.  For more information, see "[Installing and configuring {% data variables.product.prodname_desktop %}](/desktop/installing-and-configuring-github-desktop/)."