fix(package): update postcss-import to version 10.0.0 (#23)

Author: greenkeeper[bot]

package.json

@@ -10,7 +10,7 @@
   "dependencies": {
     "cssnano": "^3.7.4",
     "postcss-cssnext": "^2.7.0",
-    "postcss-import": "^9.0.0",
+    "postcss-import": "^10.0.0",
     "rucksack-css": "^0.9.1",
     "sugarss": "^0.2.0"
   },