Added type hinting+ small changes

[Siddhesh-Agarwal]

Description

• Added type hinting
• Added default values when using get() method in discord.py
• Used Black + Isort for formatting
• Replaced os.environ with os.getenv + Check so that error messages are raised in case of missing environment variables (suggestion: add python-dotenv in dependencies)

Changes Include

• Bug fix 🐛 (non-breaking change which fixes an issue)
• New feature ✨ (non-breaking change which adds functionality)
• Breaking change 😢 (fix or feature that would cause existing functionality to not work as expected)
• Refactor ⚒️ (code change that neither fixes a bug nor adds a feature)
• Tooling ⚙️ (Changes to the build process or auxiliary tools and libraries such as documentation generation)
• Performance ⚡ (code change that improves performance)
• This change requires a documentation update 📖

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[Siddhesh-Agarwal]

@Bhupesh-V Is there a chance of this being merged?