- Raise CellInvalidError when attempting to specify the wrong corners of
the cell when creating it. The x and y values should always represent
the top left and bottom right corners of the cell.
- Raise CellTooSmallError when attempting to specify a cell which is too
small to correctly draw its central point.
- Add an entrance and exit to the maze. The entrance will always
be on the top left and the exit will always be on the bottom
right.
- Add a simple GitHub actions workflow to run the Python tests.
