Update networking layer w/ CURL and emscripten impl

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

@@ -0,0 +1,82 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLOPT_HEADER
+Section: 3
+Source: libcurl
+Protocol:
+  - HTTP
+  - FTP
+  - IMAP
+  - POP3
+  - SMTP
+See-also:
+  - CURLOPT_HEADERFUNCTION (3)
+  - CURLOPT_HTTPHEADER (3)
+Added-in: 7.1
+---
+
+# NAME
+
+CURLOPT_HEADER - pass headers to the data stream
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADER, long onoff);
+~~~
+
+# DESCRIPTION
+
+Pass the long value *onoff* set to 1 to ask libcurl to include the headers
+in the write callback (CURLOPT_WRITEFUNCTION(3)). This option is
+relevant for protocols that actually have headers or other meta-data (like
+HTTP and FTP).
+
+When asking to get the headers passed to the same callback as the body, it is
+not possible to accurately separate them again without detailed knowledge
+about the protocol in use.
+
+Further: the CURLOPT_WRITEFUNCTION(3) callback is limited to only ever
+get a maximum of *CURL_MAX_WRITE_SIZE* bytes passed to it (16KB), while a
+header can be longer and the CURLOPT_HEADERFUNCTION(3) supports getting
+called with headers up to *CURL_MAX_HTTP_HEADER* bytes big (100KB).
+
+It is often better to use CURLOPT_HEADERFUNCTION(3) to get the header
+data separately.
+
+While named confusingly similar, CURLOPT_HTTPHEADER(3) is used to set
+custom HTTP headers.
+
+# DEFAULT
+
+0
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+  if(curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
+
+    curl_easy_setopt(curl, CURLOPT_HEADER, 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).