kernel-dev: Added the "writernotes" style.

(From yocto-docs rev: 5ba749bf7a169ba1eb5440f93a00a093a07641a9)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/kernel-dev/kernel-dev-style.css

@@ -730,6 +730,10 @@ div.navfooter {
   border-color: black;
 }
 
+.writernotes {
+  color: red;
+}
+
 
   /*********** /
  /  graphics  /