Document postbackHandlerName list values support

Documents wintercms/winter@37d0c36

Author: LukeTowers

backend/forms.md

@@ -762,7 +762,7 @@ Option | Description
 `fieldName` | defines a custom field name to use in the POST data sent from the data table. Leave blank to use the default field alias.
 `height` | the data table's height, in pixels. If set to `false`, the data table will stretch to fit the field container.
 `keyFrom` | the data attribute to use for keying each record. This should usually be set to `id`. Only supports integer values.
-`postbackHandlerName` | specifies the AJAX handler name in which the data table content will be sent with. When set to `null` (default), the handler name will be auto-detected from the request name used by the form which contains the data table. It is recommended to keep this as `null`.
+`postbackHandlerName` | comma-separated list of AJAX handler names with which the data table content will be sent. When set to `null` (default), the handler name will be auto-detected from the request name used by the form which contains the data table. It is recommended to keep this as `null`.
 `recordsPerPage` | the number of records to show per page. If set to `false`, the pagination will be disabled.
 `searching` | allow records to be searched via a search box. Default: `false`.
 `toolbar` | an array representing the toolbar configuration of the data table.