Superstatic configuration migration for 4.x

Author: developit

package.json

@@ -4,7 +4,7 @@
   "description": "Ready-to-go Preact starter project powered by webpack.",
   "scripts": {
     "dev": "NODE_ENV=development webpack-dev-server --inline --progress",
-    "start": "superstatic build -p ${PORT:-8080} --host 0.0.0.0 --gzip -c '{\"rewrites\": [{\"source\":\"**\",\"destination\":\"index.html\"}],\"cache_control\":{\"**\":86400}}'",
+    "start": "superstatic build -p ${PORT:-8080} --host 0.0.0.0 --gzip -c '{\"rewrites\": [{\"source\":\"**\",\"destination\":\"index.html\"}],\"headers\":[{\"source\":\"**\",\"headers\":[{\"key\":\"Cache-Control\",\"value\":\"max-age=86400\"}]}]}'",
     "prestart": "npm run build",
     "build": "NODE_ENV=production webpack -p --progress",
     "prebuild": "mkdir -p build && ncp src/assets build/assets",