Replace node-sass with dart-sass

[AnalyzePlatypus]

Closes #26 by switching to the canonical Dart Sass library.

[AnalyzePlatypus]

The current implementation (using node-sass) crashes on macOS Big Sur, which is unsupported by node-sass. This PR fixes that.

[WilNichols]

Any news here?

[nachtfunke]

Was just about to do the same. What can we do to see this merged?

[patricknelson]

Pinging @Sonaryr, would you be able to please take a look at this? 🙏 This looks like a relatively simple change. 😄

Not that I care all that much (since I don't have any dependencies on the older node-sass) but it might also make sense to implement a configuration option as well for backward compatibility (i.e. allow user to pass in their preferred compiler). That way maybe it'd see more adoption in case it breaks anything. e.g.

eleventyConfig.addPlugin(require('eleventy-plugin-sass'), {
  // ...
  compiler: require('node-sass'),
  // ...
});

[patricknelson]

Just created #32 inspired by this pull request which addresses two issues above, i.e.:

1. Fixes the dependency issue on sass and
2. Allows you to override via new compiler option in case you still wanted to use node-sass for some reason.