Downgrade postcss for backwards compatibility reasons

Author: Ben Zörb

package-lock.json

@@ -23,7 +23,7 @@
     "optimization"
   ],
   "engines": {
-    "node": "^10 || ^12 || >=14"
+    "node": ">=10"
   },
   "dependencies": {
     "@hapi/joi": "^17.1.1",
@@ -47,7 +47,7 @@
     "p-all": "^3.0.0",
     "penthouse": "^2.3.2",
     "plugin-error": "^1.0.1",
-    "postcss": "^8.1.1",
+    "postcss": "^7.0.35",
     "postcss-discard": "^1.0.1",
     "postcss-image-inliner": "^4.0.3",
     "postcss-url": "^8.0.0",