Update networking layer w/ CURL and emscripten impl

External/curl-8.17.0/docs/libcurl/curl_slist_append.md

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+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: curl_slist_append
+Section: 3
+Source: libcurl
+See-also:
+  - curl_slist_free_all (3)
+Protocol:
+  - All
+Added-in: 7.1
+---
+
+# NAME
+
+curl_slist_append - add a string to an slist
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+struct curl_slist *curl_slist_append(struct curl_slist *list,
+                                     const char *string);
+~~~
+
+# DESCRIPTION
+
+curl_slist_append(3) appends a string to a linked list of strings. The
+existing **list** should be passed as the first argument and the new list is
+returned from this function. Pass in NULL in the **list** argument to create a
+new list. The specified **string** has been appended when this function
+returns. curl_slist_append(3) copies the string. The **string** argument must
+be a valid string pointer and cannot be NULL.
+
+The list should be freed again (after usage) with
+curl_slist_free_all(3).
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *handle = curl_easy_init();
+  struct curl_slist *slist = NULL;
+  struct curl_slist *temp = NULL;
+
+  slist = curl_slist_append(slist, "pragma:");
+
+  if(!slist)
+    return -1;
+
+  temp = curl_slist_append(slist, "Accept:");
+
+  if(!temp) {
+    curl_slist_free_all(slist);
+    return -1;
+  }
+
+  slist = temp;
+
+  curl_easy_setopt(handle, CURLOPT_HTTPHEADER, slist);
+
+  curl_easy_perform(handle);
+
+  curl_slist_free_all(slist); /* free the list again */
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+A null pointer is returned if anything went wrong, otherwise the new list
+pointer is returned. To avoid overwriting an existing non-empty list on
+failure, the new list should be returned to a temporary variable which can
+be tested for NULL before updating the original list pointer.