Added another variable in _config.yml that needs customising.

README.md

@@ -85,8 +85,11 @@ please [get in touch](#getting-and-giving-help).
     Editing hints are embedded in `index.html`,
     and full instructions are in [the customization instructions][customization].
 
-4.  Edit `_config.yml` to customize certain site-wide variables, such as: `carpentry` (to tell us which carpentry workshop this is), `title` (overall title for all pages), `workshop_repo` (the URL of the workshop repository on GitHub) and `workshop_site` (the repository's GitHub Pages URL).
-
+4.  Edit `_config.yml` to customize certain site-wide variables, such as: `carpentry` (to tell us which carpentry workshop this is), `title` (overall title for all pages), `repository` (so that URLs resolve correctly both locally and on GitHub), `workshop_repo` (the URL of the workshop repository on GitHub) and `workshop_site` (the repository's GitHub Pages URL).
+
+Editing hints are embedded in `_config.yml`,
+    and full instructions are in [the customization instructions][customization].
+
 5.  Alternatively,
     if you are already familiar with Git,
     you can clone the repository to your desktop,