Update dependency postcss-value-parser to v4

Author: renovate-bot

package.json

@@ -22,7 +22,7 @@
   },
   "dependencies": {
     "postcss": "^7.0.1",
-    "postcss-value-parser": "^3.2.3",
+    "postcss-value-parser": "^4.0.0",
     "read-cache": "^1.0.0",
     "resolve": "^1.1.7"
   },