Update config.py for LazySettings issue

[kenanmasri]

I had some problem:

Error reading webpack-stats.json. Are you sure webpack has generated the file and the path is correct?

When trying to use the utils from the package inside my python apps.
It means it might have been using Django's lazy settings I think. Thus my main project's settings.py would not be available:

user_config = getattr(settings, 'WEBPACK_LOADER', DEFAULT_CONFIG)

This would in turn give the DEFAULT_CONFIG. At least in my implementation (which is templatetags specifically).

This is my code for reference

a file called templatetags/core.py

  from webpack_loader.utils import get_as_tags as webpack_loader_get_as_tags

  @register.simple_tag(name="render_bundle_prefetch")
  def do_render_bundle_prefetch(
          bundle_name, extension=None, config='DEFAULT', suffix='',
          attrs=''):
      rendered_bundle = webpack_loader_get_as_tags(
          bundle_name, extension=extension, config=config, suffix=suffix,
          attrs=attrs, is_preload=True)
      rendered_bundle = "\n".join(rendered_bundle)
      rendered_bundle = mark_safe(rendered_bundle.replace('rel="preload"', 'rel="prefetch"'))
      return rendered_bundle

Anyway this is my suggestion. I have moved everything inside load_config.