docs(announce): change default content of main.html

Author: RicardoRyn

overrides/main.html

@@ -1,5 +1,5 @@
 {% extends "base.html" %}
 
 {% block announce %}
-  <strong>📢 Announcement Bar. </strong>
+  <strong>📢 公告栏。Announcement Bar. </strong>
 {% endblock %}