Explore a command interface

[oubiwann]

Examples to look at:

• https://github.com/lemunozm/termchat
• https://github.com/rhysd/tui-textarea
• the tui user input demo

Tasks:

• Think about user input and commands (like navigating the world, chatting with players)
• Maybe entering a "chat mode"?
• Look at command parsers / tokenizers in Rust
• Think about implementing the collection of MUD commands in Rust