Create initial documentation user command

[rwblickhan]

Create a document in docs/ that lists the various options/help strings/etc that we will implement for MVP for the @rocket user command.

In particular, we will want to match the functionality of the current @rocket remove-user, @rocket view-user, @rocket edit, @rocket set, and @rocket add-user commands (but hopefully with better names!). These should probably all be implemented as subcommands or flags to the core @rocket user command.