Main feature:
- Added functionality to randomly generate a maze before the solver
solves it.
Fixes:
- Add a public method in the Cell class called wall_exists() that
returns true if a given cell wall exists (false otherwise).
Refactors:
- Added an enum type called CellWallLabel for labelling the four cell
walls.
- Added a draw() function in the CellWall class to reduce repeated code.
- Move the custom exceptions to errors.py
Tests:
- Add tests for the custom exceptions.
CI:
- Added a workflow for Forgejo Actions.
