Add `version` to `__init__.py`

[mlincett]

It is pretty common wanting to access/log a package/app version.

I wonder if (optionally?) adding:

from importlib.metadata import version

__version__ = version("km3aim")

to the __init__.py file could be a welcome improvement.

On a side note: when using poetry I had the problem that if the pyproject.toml was updated without running poetry install, importlib would not be able to pick up the change so I had to parse pyproject.toml. With uv this should no longer be a problem.