Add 2 more parameters about the volumes

[DavideViolante]

item[5] and item[6] probably (help wanted) represents the volume, add them into the APIs.

Eg for dow jones:

        [
            1645660800000,
            32830.33,
            33269.34,
            32272.64,
            33223.83,
            593186432, // volume?
            0 // volume?
        ],