Favicon support

[joe-replin]

Subject of the issue/enhancement/features

It is the one console error that is displayed in every new Adapt build. May we place the Adapt icon at the root level for starters? With future thought for the AAT, I imagine we'll need a method to change this.

• Future state: the favicon is adjustable somewhere in the AAT UI
• Quicker fix: the favicon lives in the theme and is placed at the root of the build once compiled

Expected behaviour

Use a default favicon so the error goes away.

Actual behaviour

A console error is displayed in every new Adapt build.

Screenshots (if you can)