Fix onCreatingRowSave return type to match documentation (#1311)

In documentation (https://www.material-react-table.com/docs/api/table-options) both `onCreatingRowSave` and `onEditingRowSave` should accept a function with a return type of `Promise<void> | void` but in the typings the `onCreatingRowSave` accepts only `void`.

Author: samuliasmala

packages/material-react-table/src/types.ts

@@ -1196,7 +1196,7 @@ export interface MRT_TableOptions<TData extends MRT_RowData>
     row: MRT_Row<TData>;
     table: MRT_TableInstance<TData>;
     values: Record<LiteralUnion<string & DeepKeys<TData>>, any>;
-  }) => void;
+  }) => Promise<void> | void;
   onDensityChange?: OnChangeFn<MRT_DensityState>;
   onDraggingColumnChange?: OnChangeFn<MRT_Column<TData> | null>;
   onDraggingRowChange?: OnChangeFn<MRT_Row<TData> | null>;