refactor: sasslint linter

[sQVe]

Previous implementation required one to have sass-lint globally. This
allows you to have it locally, override the executable and add options.

[sQVe]

I ran the tests on my system and it was OK. I'd love some pointers on how to solve the test issue CI is pointing out.

[w0rp]

Looks good to me. Add some documentation for the new options. Look at the ESLint options for good examples.

[sQVe]

@w0rp Making progress. The implementation tests are now passing but failing for the added docs. I'm a bit unsure on why.

[sQVe]

@w0rp Gave this a new shake. Think I managed to get everything fixed now. 👍

[neersighted]

This look good to me, and the documentation looks excellent.

One question -- there is a lot of duplicate code here, and the documentation only covers the scss version of each variable. I think I'd prefer making the sass variants into stubs over the scss versions (I don't really see why you'd want to have different options for both), or maybe just make sass into an alias of scss. @w0rp, do you have any opinion here?

[sQVe]

@neersighted 👍 I've had the exact same thoughts regarding duplication. What makes it a bit tricky is that the big difference between scss and sass makes it quite likely that you would want different options for them. I know cases where you want to specifically set a config file for legacy sass files and another for scss.

If you guys can think of a better solution I'm happy to implement it. I'd need some guidance though as I'm not super comfortable with Vimscript.

[RyanSquared]

I don't see a good way to merge the two and like you said it is definitely possible people could have different options. I think this is fine to merge as-is unless anyone else sees an obvious issue. I'll possibly get to merging this sometime over the weekend.

documentation provided