Consider adding a `base color` setting

[pascalduez]

Following @FWeinb proposal on Slack.

let the user define a base color via config and then calculate needed permutations

[KittyGiraudel]

I'd rather encourage building their own theme.

[eduardoboucas]

I think it'd be great to have the option to define a base colour. In some cases, that may be enough to get the documentation consistent with a project's branding or with other documentation pages, but having to create a theme from scratch — or even fork this one and taking care of maintaining it — is too much of a trouble to achieve that.

[lukassero]

That would be cool!

[tf]

I would also really like this.

[tf]

Creating one's own theme causes a lot of duplication. Even worse one cannot profit from improvements made to the default theme. What do you think about:

• Making Sass a dependency of this package
• Adding a configuration option which allows to supply a path to a custom variables.scss file
• If present, instead of copying over the assets directory, compile the contents of the scss files from this package together with the given variable overrides during sassdoc run.

This would give a lot of flexibility. The code could eventually even live in sassdoc-extras making it optionally available for other themes as well. Thoughts?