Adding badges CSS
Adding basic sidebar
Adding `content_or_partial` method

This method will render the section of `content` if `content_for` was called
or will look for a partial to render instead.
Use content_or_partial on main layout.

Most pages will hape a sidebar so it should be fine.
Adding a `full` layout

Make it possible to have a layout without sidebar.
Adding a route to see the regwall again.
Move header & footer styles to layout style file
Fix notice badge color
Remove header & footer css from application.css file
First problem list design
Adding simple link mixin

[ci skip]
Make sidebar categories links

[ci skip]