Fix warning with node 16 (#2347)
Fix warning with node 16 (#2347)

* Fix warning with node 16

This would fix this warning:
```
DeprecationWarning: Use of deprecated folder mapping "./dist/" in the "exports" field module resolution of the package at /path/to/node_modules/systemjs/package.json.
Update this package.json to use a subpath pattern like "./dist/*".
```

* Update package.json
systemjs/systemjs,systemjs/systemjs