Implement a concrete "Creature" entity, and place one on the screen at
the game startup for testing.
This revealed a bug with drawing when getting the maximum entity
position, but that appears to be fixed now (yay)
Add a "previous message" command, triggered via ctrl+p.
I attempted here to get the message area to still take up a row of space
post-hiding the message, but failed - should revisit that at some point
Implement messages almost the same as in the Rust version, only with
YAML instead of TOML this time, and a regular old mustache template
instead of something handrolled. Besides that, pretty much everything
here is the same.
