[BUG] Default import is broken in v3.5.0

Describe the bug As of v3.5.0, When importing as

import csv from 'fast-csv';

and using as

csv.writeToStream(stream, rowsWithHeaders, {
      headers: true,
    });

I get an error at runtime

TypeError: Cannot read property 'writeToStream' of undefined

To fix it, I could import like this :

import * as csv from 'fast-csv';

and everyting works again

To Reproduce Steps to reproduce the behavior:

1. npm install fast-csv@3.5.0
2. Here is a failing test (with jest) :

import csv from 'fast-csv';

describe('CSV issue', () => {
  test('should not throw', () => {
    expect(csv).not.toBeUndefined();
  });
});

it fails with :

 FAIL  src/api-admin/application/__tests__/repro.spec.ts
  ● CSV issue › should not throw

    expect(received).not.toBeUndefined()

    Received: undefined

      3 | describe('CSV issue', () => {
      4 |   test('should not throw', () => {
    > 5 |     expect(csv).not.toBeUndefined();
        |                     ^
      6 |   });
      7 | });
      8 | 

      at Object.<anonymous> (src/api-admin/application/__tests__/repro.spec.ts:5:21)

Expected behavior import csv from 'fast-csv'; should still work, or this should be a major version bump as it is possibly breaking callers.

Desktop (please complete the following information):

• OS: macOS
• OS Version Mojave 10.14.6
• Node Version 12.13.1

Additional context I believe the breakage is due to the changes in index.ts in :

https://github.com/C2FO/fast-csv/commit/28472e54e28888892314493aa5913b4b49f0ed52#diff-f41e9d04a45c83f3b6f6e630f10117fe

[doug-martin]

I’ve create #301 to address this.

[doug-martin]

I think documentation is a great place to start!

Ill add a some documentation about that. A longer term change would be to provide ts examples along side the js examples.

Thanks again for pointing this out!