As the character walks around the map, progressively reveal the entities
on the map to them, using an algorithm based on well known
circle-rasterizing and line-rasterizing algorithms to calculate lines of
sight that are potentially obscured by walls.
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.
