fix(css): mark as side effects

fixes #586 

see the css example in https://webpack.js.org/guides/tree-shaking/#mark-the-file-as-side-effect-free

Author: Haroenv

packages/autocomplete-theme-classic/package.json

@@ -9,7 +9,7 @@
     "name": "Algolia, Inc.",
     "url": "https://www.algolia.com"
   },
-  "sideEffects": false,
+  "sideEffects": ["*.css"],
   "files": [
     "dist/"
   ],