Allow domain branded error pages

[barlock]

Overview

As a user getting an error page, I want to see a branded error page from the site I'm looking at so that I'm not confused about what and where my browser is

Reference

• #25 - General custom error pages

Questions

• Not sure if this is possible...

Assumptions

• There seems to be a standard for root level documents like 404.html at least in Github Pages. That should be the api if at all possible

Acceptance

• Site creators can easily declare an error pages with <status_code>.html

Tasks