Suggestion: let the API accept a JSON object

If a `package.json` has already been parsed, it doesn't make sense to then have `pkg-ok` do it again:

```ts
// Override
function pkgOk(pkg: PackageJson, { fields = [], bin = [] }: Options = {})
```

Or maybe even from a string too:

```ts
function pkgOk(pkg: string, { fields = [], bin = [] }: Options = {})
```