message: Update CHANGELOG for new SigningStargateClient methods
diff: @@ -46,6 +46,8 @@ and this project adheres to
  not connect to Tendermint. This allows offline signing.
  - @cosmjs/stargate: Add `makeMultisignedTx` which allows you to assemble a
  transaction signed by a multisig account.
  +- @cosmjs/stargate: Add `delegateTokens`, `undelegateTokens` and
  + `withdrawRewards` methods to `SigningStargateClient`.
  ### Changed
  