Custom 404 page

[sumanthratna]

• https://docs.djangoproject.com/en/3.1/topics/http/views/#customizing-error-views
• https://docs.djangoproject.com/en/3.1/topics/http/views/#django.http.Http404:~:text=In%20order%20to%20show%20customized%20HTML,when%20DEBUG%20is%20set%20to%20False.

404 page that uses our design system rather than the standard boring html

should also render for nonexistent files under /static (I think?)