Update recommended sass gem to use, in README.

readme.md

@@ -44,12 +44,13 @@ If you're using Rails 6 in "API mode", you'll also need to do the following:
 //= link graphiql/rails/application.js
 ```
 
-Additionally, for Rails 6, you'll also need to add `sass-rails` gem to your Gemfile and add a `manifest.js` file for Sprockets 4 to work:
+Additionally, for Rails 6, you'll also need to add `dartsass-sprockets` gem to your Gemfile and add a `manifest.js` file for Sprockets 4 to work:
 ```
 --- add to `app/assets/config/manifest.js`
 //= link graphiql/rails/application.css
 //= link graphiql/rails/application.js
 ```
+Note that the `sassc-rails` gem is unmaintained and [breaks with the newer GraphiQL](https://github.com/rmosolgo/graphiql-rails/issues/106).
 See more details in [issue #13](https://github.com/rmosolgo/graphiql-rails/issues/13#issuecomment-640366886)
 
 ### Configuration