ethers.js support for overlord

This library contains functions and types to extend the @mountainpath9/overlord-core library for use with ethersjs.

In addition to rexporting all from @mountainpath9/overlord-core the following functions are provided:

function getProvider(ctx: TaskContext, chainId: number): Promise<Provider>;
function getSigner(ctx: TaskContext, provider: Provider, walletName: string): Promise<Signer>;
function createTransactionManager(ctx: TaskContext, signer: Signer, provider: Provider, params: TxSubmissionParams);

and a global nonce manager:

let NONCE_MANAGER: NonceManager

The TransactionManager submits transactions to the blockchain, with controls to subsequently increase the gas tip, and ultimately cancel the transaction if unsuccessful:

export interface TransactionManager {
  /**
   * Sign and submit the given transaction and wait
   * for it to be mined. This interface combines these
   * operations so that an implementation can lock the current
   * nonce until the transaction has been successfully mined.
   *
   * If the transaction fails to be mined, this will throw an
   * exception.
   */
  submitAndWait(tx: ContractTransaction): Promise<TransactionReceipt>;
}