doc: add comments on the config include custom

www/index.php

@@ -118,12 +118,14 @@ const ARCHIVARIX_INCLUDE_CUSTOM = array(
     'XPATH' => '//*[@id="twitter-2"]',
   ],
 
+  // replace the hoster information widget in the right column on all pages
   [
     'OPERATION' => 'REPLACE',
     'XPATH' => '//*[@id="text-6"]',
     'FILE' => 'hosted_by_franciliens.html',
   ],
 
+  // add a legacy banner on all pages to annonce the new blog
   [
     'OPERATION' => 'APPEND',
     'XPATH' => '//nav[contains(@class, "navbar")]',