update slider

Author: ogios

data/doc/4.widgets/1.slider.md

@@ -182,7 +182,7 @@ Monitor brightness
 
 `custom`
 
-## `interval_update`
+#### `interval_update`
 
 Array of tuples. each tuple contains `millisecond` and `shell command`:  
 `[<millisecond>, <shell_command>]`  
@@ -193,7 +193,7 @@ For `shell command`, the returned value must be a number within `[0, 1]`.
 _Type: `[[int, string]...]`_  
 _Default: `[]`_
 
-## `on_change`
+#### `on_change`
 
 Command to execute when progress changed.
 
@@ -204,7 +204,7 @@ Example: `notify-send {progress}`
 _Type: `null | string`_  
 _Default: `null`_
 
-## `event_map`
+#### `event_map`
 
 `mouse_key_ID : shell_command`