Improve Akamai CDN detection via server header

Many Akamai-served sites expose 'server: AkamaiGHost' or
'server: AkamaiNetStorage' but not the x-akamai-request-id header.

Added fallback detection that checks the server header for "akamai"
to improve detection on sites like fedex.com and adobe.com.

Author: bartTC

CF Cache Status/CF Cache Status Extension/Resources/background.js

@@ -72,6 +72,10 @@ function detectCDN(headers) {
   if (headers['cdn-cache'] || headers['cdn-pullzone']) return 'bunny';
   if (headers['x-varnish']) return 'varnish';
 
+  // Check server header for CDN hints
+  const server = (headers['server'] || '').toLowerCase();
+  if (server.includes('akamai')) return 'akamai';
+
   // Check x-cache with via header for additional hints
   if (headers['x-cache']) {
     const via = (headers['via'] || '').toLowerCase();