[ENHANCEMENT] Add more tests #18

Add more pytest tests to cover most parts of the code.

Current coverage: 50%

Todo:

• Add tests for ilanguage\Main\_ast.py
• Add tests for ilanguage\Main\_errors.py
• Add tests for ilanguage\Main\_types.py
• Add tests for ilanguage\Main\lexer.py
• Add tests for ilanguage\Main\shell.py
• Add tests for ilanguage\Modules\_core\Console.py
• Add tests for ilanguage\Modules\_core\Math.py
• Add tests for ilanguage\Modules\_core\Random.py
• Add tests for ilanguage\__init__.py
• Add tests for ilanguage\__main__.py