Setup NPM publishing

[Siegrift]

Closes #176

Rationale

Inspired by the publishing in https://github.com/api3dao/commons. I am using the old https://www.npmjs.com/package/@api3/airseeker NPM package name.

I tested this using Verdaccio locally. The following is exported:

{
  abs: [Getter],
  sleep: [Getter],
  deriveBeaconId: [Getter],
  encodeDapiName: [Getter],
  decodeDapiName: [Getter],
  deriveWalletPathFromSponsorAddress: [Getter],
  deriveSponsorAddressHashForManagedFeed: [Getter],
  deriveSponsorAddressHashForSelfFundedFeed: [Getter],
  deriveSponsorWalletFromSponsorAddressHash: [Getter],
  deriveSponsorWallet: [Getter],
  multiplyBigNumber: [Getter],
  decodeBeaconValue: [Getter],
  evmAddressSchema: [Getter],
  evmIdSchema: [Getter],
  providerSchema: [Getter],
  optionalContractsSchema: [Getter],
  gasSettingsSchema: [Getter],
  optionalChainSchema: [Getter],
  chainsSchema: [Getter],
  deviationThresholdCoefficientSchema: [Getter],
  walletDerivationTypeSchema: [Getter],
  walletDerivationSchemeSchema: [Getter],
  configSchema: [Getter]
}

[bdrhn9]

Published functions works for airseeker-admin. Thank you 🙏🏼