Table, Multi-select: Add note to docs (HDS-4273) (#2667)

Author: KristinLBradley

website/docs/components/table/table/partials/code/how-to-use.md

@@ -576,7 +576,13 @@ Add `isSelectable=true` to create a multi-select table. The `onSelectionChange`
 
 #### Multi-select table using a model
 
-This is a simple example of a table with multi-selection. Notice the `@selectionKey` argument provided to the rows, used by the `@onSelectionChange` callback to provide the list of selected/deselected rows as argument(s) for the invoked function:
+This is a simple example of a table with multi-selection. Notice the `@selectionKey` argument provided to the rows, used by the `@onSelectionChange` callback to provide the list of selected/deselected rows as argument(s) for the invoked function.
+
+!!! Info
+
+If you want the state of the checkboxes to persist after the model updates, you will need to provide an `identityKey` value.
+
+!!!
 
 ```handlebars
 <Hds::Table