underlineRgb16m method
Create String with an underline of the the specified RGB color
(forces using ANSI 16m SGR codes, even if level
is not 3)
WARNING: on some consoles without support for this, such as Android Studio,
using this will prevent ALL styles of the Chalk from appearing
Implementation
String underlineRgb16m(num red, num green, num blue) =>
(_chalk.underlineRgb16m(red, green, blue))(this);