Refactor simulator environment and add counter factory

This commit simplifies the overcooked environment by refactoring the way counters are created and managed. A new CounterFactory class is introduced, offloading logic from the environment class. In addition, the symbol to character mapping and other environment-related configurations are moved to a separate YAML file. The .gitignore file is also updated to ignore the 'playground' directory. Making these changes enhances code maintainability and readability.