deps: update dependency postcss to v8.3.11 (#835)

Author: renovate[bot]

package-lock.json

@@ -64,7 +64,7 @@
     "jest": "27.3.1",
     "ncp": "2.0.0",
     "npm-run-all": "4.1.5",
-    "postcss": "8.3.9",
+    "postcss": "8.3.11",
     "prettier": "2.4.1",
     "rimraf": "3.0.2",
     "rollup": "2.58.0",