docs: add a CNAME example for site resources

Author: mcanouil

docs/websites/website-tools.qmd

@@ -357,6 +357,16 @@ Images are the most commonly used type of resource file. If you have global imag
 ![](/images/logo.png)
 ```
 
+When publishing to a web host (*e.g.*, [GitHub Pages](docs/publishing/github-pages.qmd)), you can define a custom domain using a `CNAME` record and add it to your site.
+In this case, you can include the `CNAME` file in the resources list in your `_quarto.yml` configuration file:
+
+```yaml
+project:
+  type: website
+  resources:
+    - CNAME
+```
+
 ## Dark Mode
 
 Quarto websites can support both a light and dark mode. For example, you may use the `flatly` and `darkly` themes (which are designed to be used in tandem as dark and light appearances) as: