feat: add multi keys select to the docs (#761)

Author: stepan662

platform/translation_keys/batch_operations.mdx

@@ -16,6 +16,8 @@ First, select the keys you want to perform the batch operation on. You can do th
 After selecting one key, you can **select all keys** by clicking the "Select all" checkbox next to the batch operation dropdown list.
 When you use the "Select all" checkbox after performing a search or applying filters, it only selects all the keys that match the search query or filter conditions.
 
+> To select multiple keys, click the key checkbox while holding `shift`, which will select all keys between the current one and your last selected one
+
 Next, you can select the batch operation you want to perform from the dropdown list.
 
 <ScreenshotWrapper