Update readme comment (#22)

* Update

Replace all the comment has node-sass to dart-sass. Add PR#13 link to description in case people wonder what happened.

* Update README.md

Author: dtvn

README.md

@@ -48,7 +48,7 @@ Use [PostCSS Sass] as a plugin:
 
 ```js
 postcss([
-  require('@csstools/postcss-sass')(/* node-sass options */)
+  require('@csstools/postcss-sass')(/* dart-sass options */)
 ]).process(YOUR_CSS);
 ```
 
@@ -87,7 +87,7 @@ var postcss = require('gulp-postcss');
 gulp.task('css', function () {
   return gulp.src('./src/*.css').pipe(
     postcss([
-      require('@csstools/postcss-sass')(/* node-sass options */)
+      require('@csstools/postcss-sass')(/* dart-sass options */)
     ])
   ).pipe(
     gulp.dest('.')
@@ -112,7 +112,7 @@ grunt.initConfig({
   postcss: {
     options: {
       use: [
-        require('@csstools/postcss-sass')(/* node-sass options */)
+        require('@csstools/postcss-sass')(/* dart-sass options */)
       ]
     },
     dist: {