Add "packaging" to list of dependencies.

In a fresh venv, after installing "pip install -e caosdb-crawler", I get the following error when starting the "caosdb-crawler":

Traceback (most recent call last):
  File "(...)/venv/bin/caosdb-crawler", line 5, in <module>
    from caoscrawler.crawl import main
  File "(...)/src/caoscrawler/__init__.py", line 1, in <module>
    from .crawl import Crawler, SecurityMode
  File "(...)/src/caoscrawler/crawl.py", line 62, in <module>
    from .debug_tree import DebugTree
  File "(...)/src/caoscrawler/debug_tree.py", line 61, in <module>
    from .version import check_cfood_version
  File "(...)/src/caoscrawler/version.py", line 25, in <module>
    from packaging.version import parse as parse_version
ModuleNotFoundError: No module named 'packaging'

Seems like packaging is missing as a dependency.