EIP-7742: Add target_blob_count to block header (#7808)

Signed-off-by: Simon Dudley <simon.dudley@consensys.net>

config/src/main/java/org/hyperledger/besu/config/GenesisConfigFile.java

@@ -265,6 +265,17 @@ public class GenesisConfigFile {
         "0x0000000000000000000000000000000000000000000000000000000000000000");
   }
 
+  /**
+   * Gets target blob count.
+   *
+   * @return the target blob count
+   */
+  public Optional<String> getTargetBlobCount() {
+    // TODO SLD EIP-7742 not sure if we should use a default value here or enforce any
+    // "pragueAtGenesis" genesis file (used in devnets) to have this value
+    return JsonUtil.getValueAsString(genesisRoot, "targetblobcount");
+  }
+
   /**
    * Gets coinbase.
    *