Stage 1: Refactor codebase

[mist8kengas]

The first stage of refactoring involves small changes[^1] to the codebase that shouldn't have any known bugs.

External extensive tests and code review are highly appreciated.

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This PR also includes a contribution guide proposal.

[^1]: Small changes include but are not limited to: use better syntax, remove repetitive code, optimize statements.

[VampireChicken12]

Looks good to me thanks!

I meant to comment on the contributing.md 😆