Update DS Readme (#3707)

* update readme

tools/datastreamer/README.md

@@ -45,7 +45,7 @@ Outputs = ["stdout"]
     - Port: The data stream library requires a port, this must be a free port in the machine where the tool is running.
     - Filename: Full path and file name of the datastream to generate or query.
     - Version: It will be added to the data stream file header. Current version is 3. It is only for information, but it is recommended to properly set it to the correct value.
-    - ChainID: L2 Chain ID
+    - ChainID: L2 Chain ID. It is used during data stream files generation.
     - UpgradeEtrogBatchMNumber: Only useful for chains that started before Fork ID Etrog. This value must be the batch number of the firtst etrog batch. The reason for this is that the first batch for an upgrade to Etrog contains a transaction generated by the rollup smart contract that must be handled in a special way as it has not been sequenced by the sequencer, but synchronized from L1.
 - **StateDB Section**:
     - Database access to the StateDB of the zkEVM node where the trusted state is stored. The information to generate the datastream will be extracted from here.
@@ -88,6 +88,8 @@ All the decode options can work online, connecting to a node serving the stream,
 
 `make generate-file`
 
+Note: `Version` and `ChainID` fields from the Offline section of the config file are used during generation, so make sure they both are correct. Current Value for Version should be `3`.
+
 
 ### Get contents of Batch 1 from the local files