feat: support open RSS links in Safari (#6509)

lib/middleware/header.js

@@ -5,6 +5,7 @@ const headers = {
     'Access-Control-Allow-Methods': 'GET',
     'Content-Type': 'application/xml; charset=utf-8',
     'Cache-Control': `public, max-age=${config.cache.routeExpire}`,
+    'X-Content-Type-Options': 'nosniff',
 };
 if (config.nodeName) {
     headers['RSSHub-Node'] = config.nodeName;