add time update interval

Author: ogios

data/doc/4.widgets/2.box/1.text.md

@@ -84,6 +84,10 @@ Time zone, please refer to [https://docs.rs/chrono-tz/0.9.0/chrono_tz/enum.Tz.ht
 _Type: `null | string`_  
 _Default: `null` refers `Local`_
 
+#### `update_interval`
+
+`u64`
+
 ### `custom`
 
 #### `type*`