Pontoon: Update Chinese (China) (zh-CN) localization of Mozilla Activate

Localization authors:
- passionforlife <eloli@foxmail.com>

public/locales/zh-CN/activate.ftl

@@ -22,6 +22,8 @@ webext-document-title =
     .title = 构建您自己的 Firefox 扩展 | Activate Mozilla
 nav-activities = 活动
 nav-campaigns = 运动
+nav-events = 事件
+nav-groups = 群组
 nav-faq = 常见问题
 nav-impact = 影响
 nav-impact-form = 影响形式