Clarify requirements for code-links: repo (#1608)

Author: cwickham

docs/manuscripts/components.qmd

@@ -119,6 +119,10 @@ There are also two special values you can pass as items to `code-links`:
       code-links: repo
     ```
 
+    Quarto infers the URL for the link from the Git settings of your manuscript project. 
+    For `code-links: repo` to work, your manuscript project should be a Git repository, 
+    and have GitHub as the remote `origin`.
+
 `binder`
 
 :   Add a link to “Launch Binder” under "Code Links" if your manuscript is configured to [Use Binder](#using-binder):