[JS] Add error code mapping in JS wrapper

[TimoGlastra]

Currently it just gives you the code. I think we could add this enum (or make it an object mapping)

export enum AskarError {
  Success = 0,

  /// An unexpected error from the store backend
  Backend = 1,

  /// The store backend was too busy to handle the request
  Busy = 2,

  /// An insert operation failed due to a unique key conflict
  Duplicate = 3,

  /// An encryption or decryption operation failed
  Encryption = 4,

  /// The input parameters to the method were incorrect
  Input = 5,

  /// The requested record was not found
  NotFound = 6,

  /// An unexpected error occurred
  Unexpected = 7,

  /// An unsupported operation was requested
  Unsupported = 8,

  /// A custom error type for external integrations
  Custom = 100,
}