[IMP] documentation: update many2many_binary widget

The widget now also display an image preview for the files of MIME type "image".
A new option 'reverse_order' has been added to visually reverse the files order.

content/developer/reference/frontend/javascript_reference.rst

@@ -1202,6 +1202,8 @@ Many2many (`many2many`)
 Many2many Binary File (`many2many_binary`)
     This widget helps the user to upload or delete one or more files at the same time.
 
+    An image preview is available for files with the MIME type "image".
+
     Note that this widget is specific to the model `ir.attachment`.
 
     - Supported field types: `many2many`
@@ -1212,6 +1214,8 @@ Many2many Binary File (`many2many_binary`)
 
         (cf: ``accept`` attribute on `<input type="file" />`)
 
+    - `reverse_order`: set to `true` to add new files at the top of the list (default: `false`, new files are added at the bottom).
+
 Many2many Tags (`many2many_tags`)
     Display a `many2many` field as a list of tags.