Extend walking around the town functionality to use alternative keys

[mrfatguy]

Overview

For platforms that uses keyboard (desktop and web), please, extend #30 functionality to use a and d keys as well.

Narrative

See #30.

Acceptance Criteria

• Given that I am in the city
• When I press a or f key on the keyboard
• Then character sprite moves by one full step left or right

For remaining AC, please see #30.