doc: add maxuploadtarget to bitcoin.conf example

Introduce the maxuploadtarget option to the example bitcoin.conf file. This adds visibility for this option which is useful to those looking to configure bandwidth usage.

share/examples/bitcoin.conf

@@ -71,6 +71,12 @@
 # configuration option or the addnode RPC, which have a separate limit of 8 connections.
 #maxconnections=
 
+# Maximum upload bandwidth target in MiB per day (e.g. 'maxuploadtarget=1024' is 1 GiB per day).
+# This limits the upload bandwidth for those with bandwidth limits. 0 = no limit (default: 0).
+# -maxuploadtarget does not apply to peers with 'download' permission.
+# For more information on reducing bandwidth utilization, see: doc/reduce-traffic.md.
+#maxuploadtarget=
+
 #
 # JSON-RPC options (for controlling a running Bitcoin/bitcoind process)
 #