Update networking layer w/ CURL and emscripten impl

External/curl-8.17.0/docs/libcurl/opts/CURLOPT_HTTPPROXYTUNNEL.md

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+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_HTTPPROXYTUNNEL
+Section: 3
+Source: libcurl
+Protocol:
+  - All
+See-also:
+  - CURLOPT_PROXY (3)
+  - CURLOPT_PROXYPORT (3)
+  - CURLOPT_PROXYTYPE (3)
+Added-in: 7.3
+---
+
+# NAME
+
+CURLOPT_HTTPPROXYTUNNEL - tunnel through HTTP proxy
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPPROXYTUNNEL, long tunnel);
+~~~
+
+# DESCRIPTION
+
+Set the **tunnel** parameter to 1L to make libcurl tunnel all operations
+through the HTTP proxy (set with CURLOPT_PROXY(3)). There is a big
+difference between using a proxy and to tunnel through it.
+
+Tunneling means that an HTTP CONNECT request is sent to the proxy, asking it
+to connect to a remote host on a specific port number and then the traffic is
+just passed through the proxy. Proxies tend to white-list specific port numbers
+it allows CONNECT requests to and often only port 80 and 443 are allowed.
+
+To suppress proxy CONNECT response headers from user callbacks use
+CURLOPT_SUPPRESS_CONNECT_HEADERS(3).
+
+HTTP proxies can generally only speak HTTP (for obvious reasons), which makes
+libcurl convert non-HTTP requests to HTTP when using an HTTP proxy without
+this tunnel option set. For example, asking for an FTP URL and specifying an
+HTTP proxy makes libcurl send an FTP URL in an HTTP GET request to the
+proxy. By instead tunneling through the proxy, you avoid that conversion (that
+rarely works through the proxy anyway).
+
+# DEFAULT
+
+0
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com/file.txt");
+    curl_easy_setopt(curl, CURLOPT_PROXY, "http://127.0.0.1:80");
+    curl_easy_setopt(curl, CURLOPT_HTTPPROXYTUNNEL, 1L);
+    curl_easy_perform(curl);
+  }
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+curl_easy_setopt(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).