Add support for opting out of ANSI coloring via NO_COLOR env. variable

Cake is able to detect if ANSI coloring is supported in a number of cases, but once it detects that color is supported, there’s no way of opting out of it at the moment.

Some ideas:

• Check for the existence of an environment variable (NO_COLOR seems to be a standard) to opt out of ANSI coloring
• Add a new command-line switch e.g. --no-color and/or --color=false to opt out of ANSI coloring

---

Common options used to determine if ANSI coloring should be disabled used by some apps on GitHub:

• Command-line arguments:

  • --no-color
  • --no-colors
  • --color=false
  • --color=never

• Environment variables:

  • TERM=dumb
  • FORCE_COLOR=false
  • FORCE_COLOR=0

[patriksvensson]

@pascalberger Makes sense to respect NO_COLOR since that’s a pretty common convention. Other than that, the rest could be done in Cake.

[pascalberger]

Configuration should IMHO be possible as other configuration options through environment variable, configuration file and argument.

@patriksvensson Is this something which should be done in Spectre.CLI?