message: Add c header for the transaction fee function
diff: @@ -88,6 +88,7 @@ void cardano_transaction_builder_delete(cardano_transaction_builder *tb);
  void cardano_transaction_builder_add_output(cardano_transaction_builder *tb, cardano_txoptr *txo);
  cardano_result cardano_transaction_builder_add_input(cardano_transaction_builder *tb, cardano_txoptr *c_txo, uint64_t value);
  cardano_result cardano_transaction_builder_add_change_addr(cardano_transaction_builder *tb, cardano_address *change_addr);
  +int cardano_transaction_builder_fee(cardano_transaction_builder *tb);
  cardano_transaction *cardano_transaction_builder_finalize(cardano_transaction_builder *tb);
  cardano_transaction_finalized * cardano_transaction_finalized_new(cardano_transaction *c_tx);
  