Improve extending Custom errors

[carnakovic]

Narrowing the error type with instaceof doesn't work correctly.

import { retry, RetryError } from 'ts-retry-promise';

try {
  await retry(() => Promise.reject('test'));
} catch (error: unknown) {
  if (error instanceof RetryError) {
    // never get here
  }

  // the above doesn't work
  error.name // Error
  error instanceof Error // true
  error instanceof RetryError // false
}

Extending built-in Error type with extends ES6 keyword doesn't work correctly when the code is later transformed to ES5.

Recommend to use make-error lib for extending error types.