add security headers

website/vercel.json

@@ -25,7 +25,7 @@
  },
  {
  "key": "Content-Security-Policy",
- "value": "img-src 'self' https:;"
+ "value": "default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval' *.github.io; *.googletagmanager.com *.google-analytics.com"
  }
  ]
  }