Enforce EOL newlines in CSS files (#31174)

webapp/channels/package.json

@@ -103,7 +103,7 @@
     "@mattermost/eslint-plugin": "*",
     "@mattermost/mmjstool": "github:mattermost/mattermost-utilities#7b63833d208d482ba4a1c12230bb3e68dd9c5e5e",
     "@redux-devtools/extension": "3.2.3",
-    "@stylistic/stylelint-plugin": "2.1.0",
+    "@stylistic/stylelint-plugin": "3.1.2",
     "@testing-library/jest-dom": "5.16.4",
     "@testing-library/react": "12.1.4",
     "@testing-library/react-hooks": "8.0.1",