fix: include py.typed file

[G-Rath]

Following on from #221, if I'm understanding the docs correctly this file needs to be included in the package for mypy and co to use its types

[chrispy-snps]

@G-Rath - I don't use mypy so I'm not sure how to validate this. Are you able to do any validation on your side?

[G-Rath]

@chrispy-snps yes I've verified this resolves the issue:

(on branch for DrupalSecurityTeam/drupal-advisory-database#121)

drupal-advisory-database on  update-markdownify [$?⇕] via  v20.19.0 via 🐍 v3.13.5
❯ poetry run mypy .
scripts/generate_osv_advisories.py:19: error: Skipping analyzing "markdownify": module is installed, but missing library stubs or py.typed marker  [import-untyped]
scripts/generate_osv_advisories.py:19: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
Found 1 error in 1 file (checked 11 source files)

drupal-advisory-database on  update-markdownify [$?⇕] via  v20.19.0 via 🐍 v3.13.5
❯ touch /home/jones/.cache/pypoetry/virtualenvs/drupal-advisory-database-Cs10MxDi-py3.13/lib/python3.13/site-packages/markdownify/py.typed

drupal-advisory-database on  update-markdownify [$?⇕] via  v20.19.0 via 🐍 v3.13.5
❯ poetry run mypy .
Success: no issues found in 11 source files

[darkdragon-001]

Is anything missing to get this merged?