fish config

This is my fish config. It is designed to work on macOS and GNU/Linux, at the very least. It's unlikely that it'll be useful to anyone else, as it's very much about the way I work, but I make it available here just in case.

The key points with this config are:

• This repository is designed to be cloned in ~/.config and is designed to
  be general to all machines I work on.
• Each machine can have a ~/.config/local-fish which this configuration
  will load up. Such configurations are
  maintained locally. For example, none of my work-specific configuration is
  in here, but the ~/.config/local-fish on my work machines is held in a
  repository in work's GitLab server.