terminal: TUI library

[erak]

Description

This adds a TUI library based on tui-rs that comes with:

• generic key-value store for application properties
• common widgets and support for application specific ones
• separate render and event thread
• stacked, multi-page layout
• 2 predefined theme(s): default and with borders
• example application(s):
  • basic: example/tui.rs
  • custom widget: example/tui_widget.rs
  • re-run after internal call: example/tui_internal_call.rs

Examples

[cloudhead]

Would it make sense to maybe split the TUI functionality in its own crate? Eg. radicle-terminal-tui, which can depend on radicle-terminal. We're already struggling with build times, so it would help if this didn't add overhead to all existing crates.

[erak]

Yes, absolutely! Will take care of this.

[erak]

Closing this now in favor of #171.