[feature] support --color=auto

[Freed-Wu]

--color=never is equivalent with --color, --color=always is equivalent with --no-color, when the output is stdout, --color=auto = --color=always, when output is not stdout (such as a file), --color=auto = --color=never.

[blueyed]

Just for reference: --color is a boolean flag currently, and therefore not easily changeable into an options with arguments (at least when --color auto should/would also work as --color=auto).
Code ref:

vint/vint/linting/cli.py

Lines 101 to 102 in 471e70b

	parser.add_argument('-c', '--color', action='store_const', const=True, help='colorize output when possible')
	parser.add_argument('--no-color', action='store_const', const=True, help='do not colorize output')

Therefore color could be auto-detected maybe with neither of the flags being given maybe?

Also in this regard: support for $NO_COLOR (https://no-color.org/).