Upgrade postcss-import to latest

Author: simonsmith

package.json

@@ -26,7 +26,7 @@
     "postcss-calc": "^5.0.0",
     "postcss-custom-media": "^5.0.0",
     "postcss-custom-properties": "^5.0.0",
-    "postcss-import": "^7.1.3",
+    "postcss-import": "^8.0.2",
     "postcss-reporter": "^1.3.0",
     "read-file-stdin": "0.2.0",
     "stylelint": "^2.3.5"