Add subtractfeeamount parameter to sendmany RPC

Source: e4918316d8/src/wallet/rpcwallet.cpp (L890)

_includes/devdoc/bitcoin-core/rpcs/rpcs/sendmany.md

@@ -55,6 +55,16 @@ The `sendmany` RPC {{summary_sendMany}}
 
 {% enditemplate %}
 
+*Parameter #5---automatic fee subtraction
+
+{% itemplate ntpd1 %}
+- n: "Subtract Fee From Amount"
+  t: "boolean"
+  p: "Optional<br>(0 or 1)"
+  d: "The fee will be deducted from the amount being sent. The recipient will receive less bitcoins than you enter in the amount field. Default is false"
+  
+{% enditemplate %}
+
 *Result---a TXID of the sent transaction*
 
 {% itemplate ntpd1 %}