Add values to slotprops of datatable

[Harm-Nullix]

ItemsLength, startIndex & stopIndex are not in slot props but are really handy when making pagination your own.

https://github.com/vuetifyjs/vuetify/blob/ae7a66769543bd69bbf75761dec0baf335dd334f/packages/vuetify/src/components/VDataTable/composables/paginate.ts#L27C1-L30C27

An workaround is using the inject of the vuetify:data-table-pagination that is set inside the usePagination composable, but that is an internal working