support CF headers for metadata

[acidjazz]

Use/detect these headers

export default {
  async fetch(request, env, ctx) {
    const pairs = []
    for (var pair of request.headers.entries()) {
      pairs.push({name: pair[0], value: pair[1]})
    }
    return Response.json(pairs);
  },
};

  {
    "name": "accept",
    "value": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7"
  },
  {
    "name": "accept-encoding",
    "value": "gzip, br"
  },
  {
    "name": "accept-language",
    "value": "en-US,en;q=0.9,la;q=0.8,ja;q=0.7"
  },
  {
    "name": "cf-connecting-ip",
    "value": "2605:a601:a0ee:c700:505d:6f74:a4d:65c3"
  },
  {
    "name": "cf-ipcountry",
    "value": "US"
  },
  {
    "name": "cf-ray",
    "value": "8be95a7a5d702cb4"
  },
  {
    "name": "cf-visitor",
    "value": "{\"scheme\":\"https\"}"
  },
  {
    "name": "connection",
    "value": "Keep-Alive"
  },
  {
    "name": "host",
    "value": "bio.acidjazz.workers.dev"
  },
  {
    "name": "priority",
    "value": "u=0, i"
  },
  {
    "name": "sec-ch-ua",
    "value": "\"Chromium\";v=\"128\", \"Not;A=Brand\";v=\"24\", \"Google Chrome\";v=\"128\""
  },
  {
    "name": "sec-ch-ua-mobile",
    "value": "?0"
  },
  {
    "name": "sec-ch-ua-platform",
    "value": "\"macOS\""
  },
  {
    "name": "sec-fetch-dest",
    "value": "document"
  },
  {
    "name": "sec-fetch-mode",
    "value": "navigate"
  },
  {
    "name": "sec-fetch-site",
    "value": "cross-site"
  },
  {
    "name": "sec-fetch-user",
    "value": "?1"
  },
  {
    "name": "upgrade-insecure-requests",
    "value": "1"
  },
  {
    "name": "user-agent",
    "value": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36"
  },
  {
    "name": "x-forwarded-proto",
    "value": "https"
  },
  {
    "name": "x-real-ip",
    "value": "2605:a601:a0ee:c700:505d:6f74:a4d:65c3"
  }
]