Enable pre-commit.ci

[EwoutH]

Currently the pre-commit.ci configuration, .pre-commit-config.yaml, is a bit outdated. We could update it manually or write a custom workflow for it, but the easiest way to fix is is enable pre-commit.ci. By default, it checks weekly if pre-commit versions can be updated and if so opens a PR to do so.

It also has an option to autofix PRs, which can be a great quality of life feature.

[EwoutH]

@jorisvandenbossche Since you wrote the current pre-commit configuration, what do you think?