Say what the comment character is

doc/README.siteconf

@@ -8,6 +8,7 @@ The siteconf is read from ~/.w3m/siteconf by default.
 
 ===== The syntax =====
 
+# comment
 url <url>|/<re-url>/|m@<re-url>@i [exact]
 substitute_url "<destination-url>"
 url_charset <charset>
@@ -17,6 +18,9 @@ user_agent "string"
 
 The last match wins.
 
+Lines starting with a '#' are ignored. You can use this to annotate the
+entries.
+
 ===== Examples =====
 
 url m!^https?://([a-z]+\.)?twitter\.com/!