`uvu --no-color` has no effect

[kizdolf]

The cli arguments defines -c, --color Print colorized output (default true), allowing the option --no-color to disable output colorization.

But using it has no effect.

This is due to two things:

option is never checked for false

The option set process.env.FORCE_COLOR = '1' when true (the default) but is never set to something else.
See: https://github.com/lukeed/uvu/blob/master/bin.js#L22
Since the default is true I propose

if (opts.color) process.env.FORCE_COLOR = '1';
else process.env.FORCE_COLOR = '0';

process.env.FORCE_COLOR is never checked.

colorization is done using kleur in https://github.com/lukeed/uvu/blob/master/src/diff.js
but it does not check for process.env.FORCE_COLOR

kleur has a enabled option, which could be usefull:

if(process.env.FORCE_COLOR === '0') kleur.enabled = false

I've open #226 to fix this