Patch: save correct headers for XHR requests

[ErikOwen]

None of the headers of XHR requests are outputted when performing headless crawls with the -xhr flag set:

> echo "https://projectdiscovery.io" | katana -silent -d 2 -jsonl -headless -xhr -cs "https://projectdiscovery.io" -ob -or -timeout 30 | jq ".response.xhr_requests"
...
[
  {
    "method": "OPTIONS",
    "endpoint": "https://events.framer.com/anonymous"
  },
  {
    "method": "POST",
    "endpoint": "https://events.framer.com/anonymous",
    "body": "[{\"source\":\"framer.site\",\"timestamp\":1697650690430,\"data\":{\"type\":\"track\",\"uuid\":\"a7dd37e7-62ca-459e-fb2a-0df5891948de\",\"event\":\"published_site_pageview\",\"referrer\":null,\"url\":\"https://projectdiscovery.io/requestdemo\",\"hostname\":\"projectdiscovery.io\",\"pathname\":\"/requestdemo\",\"hash\":null,\"search\":null,\"framerSiteId\":\"70c3acc11c8a46451735095dca225b4de6121e4fabcd9bc18c7f46602f2e8e93\",\"context\":{\"framerSiteId\":\"70c3acc11c8a46451735095dca225b4de6121e4fabcd9bc18c7f46602f2e8e93\",\"origin\":\"https://projectdiscovery.io\",\"pathname\":\"/requestdemo\",\"search\":\"\"}}}]"
  }
]
...

The headers will always be null because httpreq.Header is used (see here), which uses the crawler's headers. Instead, the headers from the fetch request should be used.

Here is the output from running the same command above, but with the changes incorporated in this pull request:

> echo "https://projectdiscovery.io" | ./katana -silent -d 2 -jsonl -headless -xhr -cs "https://projectdiscovery.io" -ob -or -timeout 30 | jq ".response.xhr_requests" 
...
[
  {
    "method": "OPTIONS",
    "endpoint": "https://events.framer.com/anonymous",
    "headers": {
      "Access-Control-Request-Method": "POST",
      "Origin": "https://projectdiscovery.io",
      "Referer": "https://projectdiscovery.io/",
      "Sec-Fetch-Mode": "cors",
      "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 11_0_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36",
      "Accept": "*/*",
      "Access-Control-Request-Headers": "content-type"
    }
  },
  {
    "method": "POST",
    "endpoint": "https://events.framer.com/anonymous",
    "body": "[{\"source\":\"framer.site\",\"timestamp\":1697651222844,\"data\":{\"type\":\"track\",\"uuid\":\"a12c91e3-5b8a-6143-84a2-33352d507261\",\"event\":\"published_site_pageview\",\"referrer\":null,\"url\":\"https://projectdiscovery.io/requestdemo\",\"hostname\":\"projectdiscovery.io\",\"pathname\":\"/requestdemo\",\"hash\":null,\"search\":null,\"framerSiteId\":\"70c3acc11c8a46451735095dca225b4de6121e4fabcd9bc18c7f46602f2e8e93\",\"context\":{\"framerSiteId\":\"70c3acc11c8a46451735095dca225b4de6121e4fabcd9bc18c7f46602f2e8e93\",\"origin\":\"https://projectdiscovery.io\",\"pathname\":\"/requestdemo\",\"search\":\"\"}}}]",
    "headers": {
      "Referer": "https://projectdiscovery.io/",
      "User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 11_0_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36",
      "Accept": "*/*",
      "Accept-Language": "en",
      "Content-Type": "application/json",
      "Origin": "https://projectdiscovery.io"
    }
  }
]
...

[ErikOwen]

Can one of the maintainers review this pull request please 🙏?