chore(deps): update dependency postcss-nested to v6 (#272)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -149,7 +149,7 @@
     "npm-run-all": "^4.1.5",
     "nyc": "^15.1.0",
     "pako": "^2.0.3",
-    "postcss-nested": "^5.0.6",
+    "postcss-nested": "^6.0.0",
     "prettier": "^2.2.1",
     "prettier-plugin-pkg": "^0.17.0",
     "prettier-plugin-svelte": "^2.6.0",