CURLOPT_RANGE.3: works for SFTP as well

... and added a small example

docs/libcurl/opts/CURLOPT_RANGE.3

@@ -43,9 +43,20 @@ Pass a NULL to this option to disable the use of ranges.
 .SH DEFAULT
 NULL
 .SH PROTOCOLS
-HTTP, FTP, FILE and RTSP
+HTTP, FTP, FILE, RTSP and SFTP.
 .SH EXAMPLE
-TODO
+.nf
+curl = curl_easy_init();
+if(curl) {
+  curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
+
+  /* get the first 200 bytes */
+  curl_easy_setopt(curl, CURLOPT_RANGE, "0-199");
+
+  /* Perform the request */
+  curl_easy_perform(curl);
+}
+.fi
 .SH AVAILABILITY
 FILE since 7.18.0, RTSP since 7.20.0
 .SH RETURN VALUE