add CCI support

[tsuz]

Tested using this PineScript code

// This source code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
// © tak215

//@version=5
indicator("go-pine CCI Test", overlay = false)

openval  = array.from(11.3, 12.9, 11.0, 19.2, 18.1, 19.4, 19.1, 10.6, 18.8, 17.1)
highval  = array.from(19.7, 19.1, 18.8, 19.6, 19.5, 19.8, 19.5, 19.9, 19.0, 17.6)
lowval   = array.from(11.1, 12.3, 10.3, 11.7, 11.2, 13.5, 12.9, 10.3, 12.4, 10.0)
closeval = array.from(16.5, 18.7, 18.2, 11.9, 19.3, 14.2, 14.4, 11.0, 14.7, 10.3)
volumeval= array.from(11.6, 13.0, 13.8, 15.9, 16.8, 19.1, 14.7, 11.7, 17.4, 15.0)

vals (index) =>
    if index >= 0 and array.size(closeval) > index
        [array.get(openval, int(index)),array.get(highval, int(index)),array.get(lowval, int(index)),array.get(closeval, int(index)), array.get(volumeval, int(index))]

sum_test (index) =>
    if index >= 0 and array.size(closeval) > index
        [array.get(openval, int(index)),array.get(highval, int(index)),array.get(lowval, int(index)),array.get(closeval, int(index)), array.get(volumeval, int(index))]

// the same on pine
pine_mfi(src, volsrc, length) =>
    float upper = math.sum(volsrc * (ta.change(src) <= 0.0 ? 0.0 : src), length)
    float lower = math.sum(volsrc * (ta.change(src) >= 0.0 ? 0.0 : src), length)
    mfi = 100.0 - (100.0 / (1.0 + upper / lower))
    mfi


[o, h, l, c, v] = vals(array.size(openval) - (last_bar_index - bar_index))

hlc3v = (h + l + c) / 3

mfi = pine_mfi(hlc3v, v, 4)

cci = ta.cci(hlc3v, 4)

plot(c, color=color.yellow)

plot(cci , color=color.white)