How to sort column ASC using vue-data-table

Question

I am using https://github.com/AndreSouzaAbreu/vue-data-table.

actually i want to sort marks column in ASC.

columns: [
          {
            key: "12",
            index: 0,
            title: "Mark",
          },
          {
            key: "09",
            title: "Name",
            sortable: true,
            index: 1,
          }
    ]