no-unpublished-import no longer throws an error by default

## Steps to reproduce:

1. Run `npx gts init`
2. Use default options
3. Add the following code at the top of `index.ts`
``` ts
import * as gts from 'gts';
```
4. Run `npm run lint`

## Expected behaviour

It throws an error:

1:22 error "gts" is not published n/no-unpublished-import

## Actual behaviour

There is no error being thrown.

## Additional information

When adding `src` to the files array in the `package.json`, the behaviour is fixed, though it is debatable whether this is a desirable fix.

```json
"files": [
"build/src",
"src"
],
```