Use port 21000 and document CDN hostname requirements

deploy/nginx/raw.134333.xyz.conf

@@ -1,4 +1,4 @@
-# raw.134333.xyz -> RawMark 容器（127.0.0.1:20080）
+# raw.134333.xyz -> RawMark 容器（127.0.0.1:21000）
 
 server {
   listen 80;
@@ -16,7 +16,7 @@ server {
   error_log /var/log/nginx/raw.134333.xyz.error.log warn;
 
   location / {
-    proxy_pass http://127.0.0.1:20080;
+    proxy_pass http://127.0.0.1:21000;
     proxy_http_version 1.1;
     proxy_buffering off;
     proxy_set_header Upgrade $http_upgrade;