fix: address code review feedback (comment clarity, remove redundant static array, add CSS class)

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Co-authored-by: iaretechnician <2749183+iaretechnician@users.noreply.github.com>

modules/faq/rss_php.php

@@ -76,6 +76,7 @@ class rss_php {
             $rss = ltrim($rss);
 
             // Reject obviously non-XML content early to avoid noisy libxml warnings.
+            // Minimum well-formed XML is at least "<a/>" (4 bytes); require one more.
             if(strlen($rss) < 5 || $rss[0] !== '<') {
                 return;
             }