RSI - colour fill

This script showcases the new (overload) feature regarding the fill() function! 🥳

2 plots could be filled before, but with just 1 colour per bar, now the colour can be a gradient type.

In this example we have 2 plots
- rsiPlot , which plots the rsi value
- centerPlot, which plots the value 50 ('centre line')

Explanation of colour fill in the zone 50-80
Default when rsi > 50
- a bottom value is set at 50 (associated with colour aqua)
- and a top value is set at 80 (associated with colour red)

This zone (bottom -> top value) is filled with a gradient colour (50 - aqua -> 80 - red)

When rsi is towards 80, you see a red coloured zone at the rsi value,
while when rsi is around 50, you'll only see the colour aqua

The same principle is applied in the zone 20-50 when rsi < 50

Cheers!