✨ Package and distribute type information

From [Hypermodern Python Cookiecutter](https://cookiecutter-hypermodern-python.readthedocs.io/en/2020.6.15/guide.html?highlight=py.typed#the-initial-package):
"`py.typed` is an empty marker file, which declares that your package
supports typing and is distributed with its own type information (PEP
561). This allows people using your package to type-check their Python
code against it."

See:
- [PEP-561](https://www.python.org/dev/peps/pep-0561/)
- [Reference implementation: `aws-lambda-powertools-python`](aws-powertools/powertools-lambda-python#237)
- [Implementation Explanation](python-poetry/poetry#1338 (comment))

Author: TeoZosa

{{cookiecutter.project_slug}}/pyproject.toml

@@ -7,6 +7,7 @@ license = "Apache-2.0"
 readme = "README.md"
 repository = "{{cookiecutter.remote_vcs_host}}/{{cookiecutter.remote_vcs_username}}/{{cookiecutter.project_slug}}"
 homepage = "{{cookiecutter.remote_vcs_host}}/{{cookiecutter.remote_vcs_username}}/{{cookiecutter.project_slug}}"
+include = ["{{cookiecutter.package_name}}/py.typed"]
 classifiers = [
     "Intended Audience :: Developers",
     "License :: OSI Approved :: Apache Software License",