feat: Support Batch (#2162)

fixes #2161.

- Tested locally to confirm that Clio forwards Batch transactions
correctly.

src/data/AmendmentCenter.hpp

@@ -139,6 +139,7 @@ struct Amendments {
     REGISTER(DeepFreeze);
     REGISTER(PermissionDelegation);
     REGISTER(fixPayChanCancelAfter);
+    REGISTER(Batch);
 
     // Obsolete but supported by libxrpl
     REGISTER(CryptoConditionsSuite);

src/rpc/RPCCenter.cpp

@@ -85,6 +85,7 @@ forwardedRpcs()
         "channel_authorize",
         "channel_verify",
         "simulate",
+        "batch"
     };
     return kFORWARDED_RPCS;
 }