docs: clarify config file creation in Pages quickstart (#44821)

Co-authored-by: Sharra-writes <sharra-writes@github.com>

Author: royy92

content/pages/quickstart.md

@@ -38,6 +38,7 @@ In this guide, you'll create a user site at `<username>.github.io`.
 By default, the title of your site is `username.github.io`. You can change the title by editing the `_config.yml` file in your repository. You can also add a description for your site.
 
 1. Click the **Code** tab of your repository.
+1. In the file list, check whether `_config.yml` exists. If it does not exist, create a new file named `_config.yml`.
 1. In the file list, click `_config.yml` to open the file.
 1. Click {% octicon "pencil" aria-label="The edit icon" %} to edit the file.
 1. The `_config.yml` file already contains a line that specifies the theme for your site. Add a new line with `title:` followed by the title you want. Add a new line with `description:` followed by the description you want. For example: