Start a FAQ page

* Add a HighVoltage page at `/faq`
* Add a link to the footer of the landing page
* Use root URIs for pages with the `config.route_drawer` setting in HighVoltage

Minor:
* Move styles for anchor tags from `_base` into the more specific `_header` where it used

https://trello.com/c/h9zfaC9l/386-add-an-faq

Suggest using Rubocop locally instead
Link to FAQ on landing page

* Override HighVoltage controller to skip authentication