Add --colour/--no-colour alias to --color/--no-color

[Shivansh-007]

color is the preferred spelling in American English while in British English, colour is preferred. A lot of people use colour (me being one of them) and there is no reason to not support --colour and make them use --color.

[github-actions]

diff-shades reports zero changes comparing this PR (7d0bd72) to main (3905173).

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What is this? | Workflow run | diff-shades documentation

[isidentical]

Are there any other console tools which alias them together? (just looked a up a few, like pytest which also has --color but no --colour, or pylint which has colorized but not colourized).

[felix-hilden]

Thanks! I think this is nice, but I'd like it even more if the aliases would be hidden because it will reduce some clutter and still helps with the typo to silently accept both. But I'm not strong on that. Also not strong on including this if other maintainers disagree, but I think it's a nice touch.

Jason's screen shot from the new help:

[Shivansh-007]

Are there any other console tools which alias them together? (just looked a up a few, like pytest which also has --color but no --colour, or pylint which has colorized but not colourized).

Not any that I know of.

[JelleZijlstra]

I'd rather not do this. It complicates the CLI and it's not like "color" won't be understood by people who prefer the British spelling.