feat: Update get-higress.sh to include descriptions of file storage (#492)

tools/get-higress.sh

@@ -69,8 +69,9 @@ outputUsage() {
   echo "Usage: $(basename -- "$0") [DIR] [OPTIONS...]"
   echo 'Install Higress (standalone version) into the DIR (the current directory by default).'
   echo '
- -c, --config-url=URL       URL of the Nacos service 
-                            format: nacos://192.168.0.1:8848
+ -c, --config-url=URL       URL of the config storage
+                            Use Nacos with format: nacos://192.168.0.1:8848
+                            Use local files with format: file://opt/higress/conf
      --use-builtin-nacos    use the built-in Nacos service instead of
                             an external one
      --nacos-ns=NACOS-NAMESPACE