Method rename

src/danfojs-base/shared/types.ts:294–294

(
        mapper: object,
        options?: {
            axis?: 0 | 1
            inplace?: boolean
        }
    )

    ): DataFrame | void
    nUnique(axis: 0 | 1): Series
    rename(
        mapper: object,
        options?: {
            axis?: 0 | 1