[Feature request] Custom footer action for Select / MultiSelect (beyond Select all / Reset)

[MontseTelefonica]

Currently, the footer/action area of MultiSelect only exposes two fixed actions: "Select all" and "Reset." Select has no equivalent footer action row at all.

Requested change:

• Expose a generic way to add one or more custom action rows to the end of the options list / footer, for both Select and MultiSelect.
• The action itself should be arbitrary and defined by the consumer (e.g. via a prop such as footerActions or a render prop), not hardcoded to a specific behavior. Examples of actions a consumer might want: "Add new," "Manage options," "Refresh list," "Import," etc.
• This is about extensibility of the footer/action area, not a specific built-in "create item" feature. The component should not assume what the custom action does — it should just render it and call the provided handler when clicked.

Example (illustrative only, not the actual request):
One possible custom action a consumer could implement with this API is an "Add item" row that opens a drawer to create a new option (see attached mockups). This is just one example of what the generic footer-action API would enable — the request itself is for the extensibility point, not for a built-in creation flow.

Use case: any scenario where "Select all" / "Reset" are not enough and the consumer needs one more action at the end of the list — for example, adding items, managing the underlying dataset, or triggering a related workflow — without having to fork or override the component internals.