USWDS-Compile - Feature: Allow users to configure Sass options

[mahoneycm]

Is your feature request related to a problem? Please describe.

Follow-up to #131

Currently, we specify a few settings that allow users to customize the Sass compilation (see README additional settings). Sass JS API offers additional options that give more control over the way Sass compiles styles.

Describe the solution you'd like

Ideally, we'll set good defaults but allow users to pass a map of Sass options that would then be passed into our Sass scripts.

Describe alternatives you've considered

No response

Additional context

Suggestion provided by @mdmower-csnw

I don't mean to rock the boat as this is an appreciated feature, but I think it's worth pointing out that there are other open issues that could be solved at the same time by simply allowing users to configure sass options. The approach I took in the fork we're using not only silences deprecations by default (i.e. good out of box experience), but it also:

1. let's users fine-tune their deprecation notice preferences
2. could satisfy USWDS-Compile - Feature: Allow users to define SASS output style #80 if a restriction I put in place is removed
3. (I think) could satisfy USWDS-Compile - Feature: Ability to specify external packages #59 with a bit of effort in handling includes

Code of Conduct

• I agree to follow this project's Code of Conduct.
• I checked the current issues for duplicate feature requests.