Add more pre-commit hooks

[kurtmckee]

This PR introduces the following changes:

• Add new pre-commit hooks to sort imports, lint the code using flake8, and check the Dependabot config file schema.
• Auto-fix import ordering by running pre-commit run -a
• Manually fix lint errors that flake8 caught (in this case, line length and whitespace issues)

[alexprengere]

Thanks, although I have a personal preference for ruff instead of flake8, I agree that this is better than the current state.