Add --version support

[acoffman]

I was trying to see if the version of civicpy installed on the new civic VM was correct, and realized there's no --version support. This adds that:

❯ ./venv/bin/civicpy --help
Usage: civicpy [OPTIONS] COMMAND [ARGS]...

Options:
  --version   Show the version and exit.
  -h, --help  Show this message and exit.

Commands:
  annotate-vcf  Annotate a VCF with information from CIViC
  create-vcf    Create a VCF file of CIViC variants
  update        Updates CIViC content from server and stores to local...

❯ ./venv/bin/civicpy --version
civicpy, version 4.0.1

Unrelated, but notable, I was not able to get backports-datetime-fromisoformat to install locally no matter what I tried. (I did only spend like 10 mins looking into it though).

Based on the README its "A backport of Python 3.11's datetime.fromisoformat methods to earlier versions of Python 3."

I'm guessing its too early to drop 3.10 support since it's not technically EOL yet, but once it is, maybe we should drop support for it and get rid of that dependency?