Add CI

[maxmynter]

Set up a first version of a CI for the jobs repo.
Implements automated tests and running the pre-commit on pull request and push.
Largely inspired but reduced from what we have at nnbench.

[nicholasjng]

The definition likely needs to become AnyPath = Union[str, os.PathLike[str], Path]. (If we even need the Path to begin with - let's check)

EDIT: This suggests that Union[str, PathLike[str]] is the way, endorsed by typeshed: https://stackoverflow.com/questions/69673650/os-pathlikeany-vs-os-pathlikestr

PathLike itself is available since 3.6, so we're good. https://docs.python.org/3/library/os.html#os.PathLike

[maxmynter]

To stay compliant with Python 3.9, i

• Migrated the TypeAlias to Union
• Make the slots argument of the dataclass dependent of its availability in Python 3.10 (see here)
• Future imports

Also made the dataclasses frozen, as a config should not change.

[nicholasjng]

Needs a few more from __future__ import annotations imports, otherwise we're good!