translate the index page for policies (#5492)

content/zh/docs/concepts/policies/index.md

@@ -1,16 +1,16 @@
 ---
-title: Policies
-description: Describes Istio's policy management functionality.
+title: 策略
+description: 描述 Istio 的策略管理功能。
 weight: 30
 keywords: [policy,policies]
 ---
 
-Istio lets you configure custom policies for your application to enforce rules at runtime such as:
+Istio 允许您为应用程序自定义策略，用以在运行时强制执行相应的规则，例如：
 
-- Rate limiting to dynamically limit the traffic to a service
-- Denials, whitelists, and blacklists, to restrict access to services
-- Header rewrites and redirects
+- 限流用于动态限制服务流量
+- Denials、白名单和黑名单用于限制服务的访问
+- Header 的重写和重定向
 
-Istio also lets you create your own [policy adapters](/docs/tasks/policy-enforcement/control-headers) to add, for example, your own custom authorization behavior.
+Istio 还允许您创建自己的 [策略适配器](/zh/docs/tasks/policy-enforcement/control-headers)，比如，您自定义的授权行为。
 
-You must [enable policy enforcement](/docs/tasks/policy-enforcement/enabling-policy) for your mesh to use this feature.
+您必须为您的服务网格 [启用策略实施](/zh/docs/tasks/policy-enforcement/enabling-policy) 以后才能使用此功能。