in the template code of example

• https://github.com/owais/django-webpack-loader#multiple-webpack-projects

there is the following code

<!-- add some extra attributes to the tag -->
{% render_bundle 'main' 'js' 'DEFAULT' attrs='async chatset="UTF-8"'%}

attribute charset is deprecated according to

• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#Deprecated_attributes

note: chatset in your example, due to a typo.