README: Add usage example

Add an example to show how the extension works.

1 files changed, 14 insertions, 0 deletions

diff --git a/README.md b/README.md
index e5a9cd3..7a64fc0 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,20 @@ experience.
 
 
 ## Usage
+Let's say we want to modify the font of an article on `www.example.com`. Add an
+`www.example.com.css` file in the extension's `css/` directory:
+
+``` css
+/* legibility/css/www.example.com.css */
+article {
+	font: 18px/1.7em Georgia !important;
+}
+```
+
+Upon reloading the page, the custom stylesheet should now be applied.
+
+Stylesheets must use a filename matching the website's domain (including
+subdomains), and terminated by a `.css` extension.
 
 
 ## Install