Multi network transaction sign data: abstract Transaction class

[sadiabbasi]

Acceptance criteria:

• [ ] Create an abstract class named Transaction that acts as the base for different network transactions.
• [ ] Implement subclasses PangeaTransaction and EthereumTransaction to handle transactions specific to Pangea and Ethereum networks.

abstract class Transaction {
  // data for transaction (depends on network

  // Check if account exists and if not create the account, returns the account name
  abstract getOrCreateAccount(privateKey: PrivateKey): string
  // e.g. use https://hyperion.docs.eosrio.io/api/v2/#v2stateget_key_accounts for Antelope networks

  // Uses SDK from network to sign transaction, sends to network, returns transaction ID
  abstract signTransactionAndSendToNetwork(): string
}