Improve Content transformation docs

h5bp/web_performance/content_transformation.conf

@@ -4,7 +4,8 @@
 
 # Prevent intermediate caches or proxies (such as those used by mobile
 # network providers) and browsers data-saving features from modifying
-# the website's content using the `cache-control: no-transform` directive.
+# the website's content using the `no-transform` directive for
+# `Cache-Control` header.
 #
 # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
 # https://tools.ietf.org/html/rfc7234#section-5.2.2.4