Implement a map walker MVP

[milonoir]

Given a random game map that spans over the terminal screen in all directions, one must be able to walk every tile of that map using the arrow keys (or other directional keys). The player is shown as a @ character in the middle of the screen. As the player moves the map should scroll underneath. When the edge of the map becomes visible on screen, scrolling should stop and the player should move towards the edge. When the player reaches the edge, further movement to that direction is blocked (no wrapping). There should be no blocking tiles on the map at this point.