Add logo to hamburger menu

We should add a logo to the hamburger menu in this dead space. It would probably be best that this is configurable, but defaults to logo.png for now. Different sites have different types of logos so this isn't a one size fits all solution. I'd almost say instance/thumbnail.jpeg is the right solution but I fear this image size is too big for this area and rendering a larger logo file here in a smaller space is wasteful. As this is usually filled with an avatar, something around 150x150 might make sense.