Add the agent

[MinimalistSwan]

After making the maze, an agent should be able to walk through it now:

• The agent has to be able to move up, down, left, and right.
• It should be recognised when the agent hits a wall.
• The agent's total steps before reaching the end position should be counted.
• It has to be ensured that the agent tries to get to the sub-goal before reaching the end goal.