Add npm run lint:css command to run Sass linting

circle.yml

@@ -11,8 +11,8 @@ test:
   override:
     - flake8 wagtail
     - isort --check-only --diff --recursive wagtail
-    - npm run lint
-    - scss-lint
+    - npm run lint:js
+    - npm run lint:css
     - python -u runtests.py
     - npm run test:unit:coverage -- --runInBand
     - npm run build

docs/contributing/css_guidelines.rst

@@ -48,7 +48,7 @@ Then run the linter from the wagtail project root:
 
 .. code-block:: console
 
-    $ scss-lint
+    $ npm run lint:css
 
 The linter is configured to check your code for adherance to the guidelines below, plus a little more.
 

package.json

@@ -82,6 +82,7 @@
     "watch": "webpack --config ./client/webpack/dev.config.js & gulp watch",
     "start": "npm run watch",
     "lint:js": "eslint --max-warnings 16 ./client",
+    "lint:css": "scss-lint",
     "lint": "npm run lint:js",
     "test": "npm run test:unit",
     "test:unit": "jest",