add topic frontmatter to articles (#18245)

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

@@ -15,6 +15,11 @@ versions:
   free-pro-team: '*'
   enterprise-server: '*'
   github-ae: '*'
+topics:
+  - pull requests
+  - issues
+  - notifications
+  - accounts
 ---
 
 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 %}