Samuel Yow

Added Heat Index calculation method based on https://github.com/adafruit/DHT-sensor-library/blob/master/DHT.cpp Heat index formula can be viewed at https://byjus.com/heat-index-formula/

Add var-XX vars for easy modification of colours of specific prefixes

2

Allow users to modify the colour of specific prefixes by changing the variable `var-XX` rather than the colors of specific variables.