Using monospace in docs

I’m trying to add an ascii diagram to a @moduledoc, but when I generate the docs using ex_docs’s mix docs, the output doesn’t look well because of the non-monospace font it’s using.

Is there any way I can tell the docs to use a monospace font here?

      ┌──────┐
      │ User │
      └──────┘
          ◆
          │
      ┌──────────┐
      │ Settings │
      └──────────┘