[⬆️] Precommit Hooks

[npham-dev]

• Installs pre-commit for formatting and (potentially) linting
• Increases minimum python version to 3.9 from 3.8 (Poetry checks out, this was a necessity to install pre-commit)
• Adds an extra installation step in the README

Example of workflow:

I'm doing this first and then moving onto adding type annotations/linting because the diff created by formatting is pretty large and I don't want to accidentally cause a breaking change that goes under the radar. Additionally, formatting files is a fairly cheap process that won't interfere with commits or waste GitHub action minutes (I'm not sure if this is a paid or free org, but either way precommits are free).