Added help text for chainwork value

src/rpcblockchain.cpp

@@ -384,6 +384,7 @@ UniValue getblock(const UniValue& params, bool fHelp)
             "  \"nonce\" : n,           (numeric) The nonce\n"
             "  \"bits\" : \"1d00ffff\", (string) The bits\n"
             "  \"difficulty\" : x.xxx,  (numeric) The difficulty\n"
+            "  \"chainwork\" : \"xxxx\",  (string) Expected number of hashes required to produce the chain up to this block (in hex)\n"
             "  \"previousblockhash\" : \"hash\",  (string) The hash of the previous block\n"
             "  \"nextblockhash\" : \"hash\"       (string) The hash of the next block\n"
             "}\n"