Add documentation for except keyword for item action placement (#1330)

* Add documentation for `except` keyword for item action placement

* Update guides/actions/item-actions.md

Co-authored-by: Copilot <[email protected]>

* Add space

---------

Co-authored-by: Copilot <[email protected]>

Author: Flo0807

guides/actions/item-actions.md

@@ -77,12 +77,14 @@ See `Backpex.ItemAction` for a list of all available callbacks.
 
 ## Placement of Item Actions
 
-Item actions can be placed in the resource table or at the top of it. You can specify the placement of the item action by using the `only` key.
+Item actions can be placed in the resource table or at the top of it. You can specify the placement of the item action by using the `only` and `except` keys.
 
-The only key must provide a list and accepts the following options
+The `only` key is used to include specified placements, meaning the item action will only appear in the specified locations. In contrast, the `except` key is used to exclude specified placements, meaning the item action will appear in all locations except those specified.
 
-* `:row` - display an icon for each element in the table that can trigger the Item Action for the corresponding element
-* `:index` - display a button at the top of the resource table, which triggers the Item Action for selected items
+The `only` and `except` keys must provide a list and accept the following options:
+
+* `:row` - displays an icon for each element in the table, clicking it triggers the item action for the corresponding element
+* `:index` - displays a button at the top of the resource table, clicking it will trigger the item action for selected items
 
 The following example shows how to place the `show` item action on the index table rows only.