Variability Channel Index (by vitelot)

This is a momentum, trend, as well as a divergence indicator.
It is similar to CCI, though it is based on a slow and fast EMA in connection to ATR, which
allows to interprete it easily.
Both EMAs and ATR have customisable period.
Further explanation and basic usage can be found in the comment section inside the script.

릴리즈 노트:

Changed the arbitrary OS/OB levels in a dynamical and self consistent way involving
the standard deviation of VCI itself, which is also more statistically sound.
No tuning required anymore apart the usual lookback periods.