Feature Request: status bar

I am using your nice library for a dashboard and one feature I am missing a lot if the ability to have a single 1-character status bar at the bottom (like tmux) to show some help, hot-keys, etc.

I may be able to send a patch myself, but until I dig into it, I track it here.

The issue names no file, test, or entry point. Start by tracing how termui lays out and renders its terminal dashboard, then determine where a one-character bottom bar would fit and how it should expose help or hotkeys. Done means the bar can display that content without disrupting the dashboard.

Written by the indexing model from the issue text.